Forming size compositions, glass fibers coated with the same and fabrics woven from such coated fibers

ABSTRACT

The present invention provides coated fiber strand comprising at least one fiber having a residue of an aqueous forming size composition applied to at least a portion of a surface of the at least one fiber, the aqueous forming size composition comprising: (a) at least one starch; (b) at least one film-forming material; (c) at least one lubricant; and (d) a plurality of discrete particles that provide interstitial space between the at least one fiber and at least one adjacent fiber sufficient to allow wet out of the fiber strand. In one embodiment of the invention, the fibers are glass fibers, the at least one starch comprises an oleophobic starch, the at least one film-forming material comprises a N-vinyl amide polymer, the at least one lubricant comprises an ester, and the particles are dimensionally stable particles selected from polymeric organic materials, non-polymeric organic materials, polymeric inorganic materials, non-polymeric inorganic materials, composite materials and mixtures thereof. In one non-limiting embodiment of the invention, the particles comprise hexagonal boron nitride particles and/or hollow particles formed from a copolymer of styrene and acrylic monomer.  
     The present invention also provides a fabric incoporating the coated fabric strand and an electronic support and an electronic circuit board incorporating the fabric.

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 60/183,605 filed Feb. 18, 2000.

[0002] This invention relates generally to aqueous forming size compositions for treating glass fibers including at least one starch; at least one film forming material; at least one oil, wax or other lubricant, and selected discrete, dimensionally stable particles.

[0003] Typically, the surfaces of glass fibers are coated with a size composition during the forming process to protect the glass fibers from interfilament abrasion. As used herein, the. terms “size” or “sizing” means the aqueous forming size composition applied to glass fibers immediately after formation of the glass fibers. Such forming size compositions typically include as components film-formers, lubricants, coupling agents, emulsifiers, antioxidants, ultraviolet light stabilizers, colorants, antistatic agents and water, to name a few.

[0004] Sized or treated glass fibers are typically gathered into a strand, wound to form a forming package, and dried. Optionally, a secondary coating can be applied to the strands. The strands can be twisted into a yarn or bulked. Twisted strands can be used as fill or warp yarn.

[0005] The forming sized strands can be processed into a wide variety of configurations, for example braids, roving, knits, tapes, chopped and continuous strand mats, and woven and non-woven fabrics, useful in many applications, such as cloth for printed circuit boards for the computer industry, knits for orthopedics or overwrap reinforcements for optical fiber cables, for example.

[0006] In a weaving operation, the strands must withstand rigorous processing conditions while maintaining various properties such as low broken filaments, which can accumulate at contact points such as guide eyes and tensioning devices, low strand tension, and high Liability and low insertion time in weaving. Insertion time is the time it takes from the start of the weaving cycle for fill yarn to traverse the width of the fabric and pass the selvage, or edge, of the opposite side of the fabric from the air jet nozzle of the loom. Fliability refers to the amount of yarn delivered in a specified time through a loom air jet nozzle held at a fixed air pressure.

[0007] In addition, since the weaving process can be quite abrasive to the fiber glass yarns, those yarns used as warp yarns are typically subjected to a secondary coating step prior to weaving, commonly referred to as “slashing”, to coat the warp yarns with an abrasion resistance coating (commonly referred to as a “slashing size”) to help minimize abrasive wear of the glass fibers. A commanly used slashing size is polyvinyl alcohol (PVA). The slashing size is generally applied over the forming size that was previously applied to the glass fibers during the fiber forming operation. As a result, if slashing size is required, the yarn must also provide adequate penetration of the slashing size into the strand.

[0008] When glass fibers and glass fiber fabrics are used as reinforcement for composites or laminates, for example in printed circuit board applications, it is important that any coating materials on the fibers be compatible with the polymeric matrix material into which the fiber strands are incorporated, i.e. the materials do not require removal prior to incorporation into the matrix material. However, many sizing components are not compatible with the polymeric matrix materials and can adversely affect adhesion between the glass fibers and the polymeric matrix material. For example, starch, which is a commonly used sizing component for textile fibers, is generally not compatible with polymeric matrix material. In addition, typical slashing sizes are also not generally compatible with the polymeric matrix materials. As a result, these incompatible materials must be removed from the fabric prior to impregnation with the polymeric matrix material.

[0009] The removal of such non-resin compatible sizing materials, i.e., de-greasing or de-oiling the fabric, can be accomplished through a variety of techniques. The removal of these non-resin compatible sizing materials is most commonly accomplished by exposing the woven fabric to elevated temperatures for extended periods of time to thermally decompose the sizing(s) (commonly referred to as heat cleaning). A conventional heat cleaning process involves heating the fabric at 380° C. for 60-80 hours. Other methods of removing sizing materials have been tried, such as water washing and/or chemical removal.

[0010] When glass fibers are used as reinforcement for printed circuit board applications, and in particular woven glass fabrics, in addition to the properties discussed above, the fabrics must also provide effective size removal in heat cleaning (if heat cleaning is required) and adequate penetration of resin materials during fabric impregnation. Overwrap reinforcements for optical fiber cables also must meet stringent requirements in view of the severe service conditions to which they are exposed.

[0011] It would be advantageous to provide a forming size composition that would facilitate penetration of the fiber bundles by a slashing size, if a slashing size is required, and could reduce, and possibly eliminate, the need to apply a slashing size by providing adequate abrasion resistance during weaving. In addition, it would be advantageous to provide a forming size composition having selected constituents that remain on the fibers and/or within the fiber bundles after heat cleaning, wherein the selected constituents are compatible with the resin applied to the fibers, would facilitate good penetration of the resin when applied to the fiber strand bundles, and provide protection to the fibers during subsequent processing.

SUMMARY OF THE INVENTION

[0012] The present invention provides coated fiber strand comprising at least one fiber having a residue of an aqueous forming size composition applied to at least a portion of a surface of the at least one fiber, the aqueous forming size composition comprising: (a) at least onestarch; (b) at least one film-forming material; (c) at least one lubricant; and (d) a plurality of discrete particles that provide interstitial space between the at least one fiber and at least one adjacent fiber sufficient to allow wet out of the fiber strand. In one embodiment of the invention, the fibers are glass fibers, the at least one starch comprises an oleophobic starch, the at least one film-forming material comprises a N-vinyl amide polymer; the at least one lubricant comprises an ester, and the particles are dimensionally stable particles selected from polymeric organic materials, non-polymeric organic materials, polymeric inorganic materials, non-polymeric inorganic materials, composite materials and mixtures thereof. In one non-limiting embodiment of the invention, the particles comprise hexagonal boron nitride particles and/or hollow particles formed from a copolymer of styrene and acrylic monomer.

[0013] The present invention also provides a coated fiber strand comprising at least one fiber having a residue of an aqueous forming size composition applied to at least a portion of a surface of the at least one fiber, the aqueous forming size composition comprising: (a) at least one starch; (b) at least one film-forming material; (c) at least one lubricant; and (d) a plurality of discrete particles having a Mohs hardness of no greater than that of the at least one fiber.

[0014] The present invention also provides a fabric comprising a plurality of fiber strands comprising at least one fiber having a residue of an aqueous forming size composition applied to at least a portion of a surface of the at least one fiber, the aqueous forming size composition comprising: (a) at least one starch; (b) at least one film-forming material; (c) at least one lubricant; and (d) a plurality of discrete particles that provide interstitial space between the at least one fiber and at least one adjacent fiber sufficient to allow wet out of the fiber strand.

[0015] The present invention also provides an electronic support comprising the fabric.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] The aqueous forming size composition of the present invention provides glass fiber strands having a variety of advantageous properties, including low broken filaments, low strand tension, adequate solution penetration during slashing and resin impregnation, and high fliability and low insertion time during weaving. Glass fiber strands treated with the aqueous forming size composition of the present invention can withstand a wide variety of further processing operations such as twisting, chopping, forming into a bundle, roving, chopped mat or continuous strand mat or weaving or knitting into a cloth. Such strands are useful in a wide variety of applications, such as cloth for printed circuit boards, knits for orthopedics, and overwrap reinforcements for optical fiber cables. In addition, retaining selected components of the forming size composition on the fabric and incorporating the fabric into prepregs and laminates for electronic supports, such as printed circuit boards, can potentially improve selected properties of the prepregs, laminates and printed circuit boards, such as drillability, i.e. reduced drill tip wear and/or improved drilled hole location accuracy. More particularly, selected components of the forming size composition of the present invention can function as a lubricant during the drilling operation and/or maintain desired interstitial spacing between adjacent strand fibers. As used herein, “electronic support” means a structure that mechanically supports and/or electrically interconnects elements including but not limited to active electronic components, passive electronic components, printed circuits, integrated circuits, semiconductor devices and other hardware associated with such elements, such as but not limited to connectors, sockets, retaining clips and heat sinks.

[0017] For the purposes of this specification, other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0018] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0019] As used herein, the term “strand” means a plurality of individual fibers, i.e., at least two fibers, and the strand can comprise fibers made of different fiberizable materials (the bundle of fibers can also be referred to as “yarn”). As used herein, the term “fiber” means an individual filament. Although not limiting the present invention, the fibers have an average nominal fiber diameter ranging from 3 to 35 micrometers.

[0020] The fibers in the present invention can be formed from any type of fiberizable material known to those skilled in the art including fiberizable inorganic materials, fiberizable organic materials and mixtures of any of the foregoing. The inorganic and organic materials can be either man-made or naturally occurring materials. One skilled in the art will appreciate that the fiberizable inorganic and organic materials can also be polymeric materials. As used herein, the term “polymeric material” means a material formed from macromolecules composed of long chains of atoms that are linked together and that can become entangled in solution or in the solid state¹. As used herein, the term “fiberizable” means a material capable of being formed into a generally continuous filament, fiber, strand or yarn.

[0021] In one non-limiting embodiment of the present invention, the fibers are formed from an inorganic, fiberizable glass material. Fiberizable glass materials useful in the present invention include, but are not limited to those prepared from fiberizable glass compositions such as “E-glass”, “A-glass”, “C-glass”, “D-glass”, “R-glass”, “S-glass”, and E-glass derivatives. As used herein, “E-glass derivatives” means glass compositions that include minor amounts of fluorine and/or boron, and preferably are fluorine-free and/or boron-free. Furthermore, as used herein, “minor amounts of fluorine” means less than 0.5 weight percent fluorine, preferably less than 0.1 weight percent fluorine, and “minor amounts of boron” means less than 5 weight percent boron, preferably less than 2 weight percent boron. Basalt and mineral wool are examples of other fiberizable glass materials useful in the present invention. In one non-limiting embodiment of the present invention glass fibers are formed from E-glass or E-glass derivatives. Such compositions are well known to those skilled in the art and further discussion thereof is not believed to be necessary in view of the present disclosure. For additional information relating to glass compositions and methods of forming the glass fibers, see K. Loewenstein, The Manufacturing Technology of Continuous Glass Fibres, (3d Ed. 1993) at pages 30-44, 47-103, and 115-165; U.S. Pat. Nos. 4,542,106 and 5,789,329; and IPC-EG-140 “Specification for Finished Fabric Woven from ‘E’ Glass for Printed Boards” at page 1, a publication of The Institute for Interconnecting and Packaging Electronic Circuits (June 1997), which are specifically incorporated by reference herein.

[0022] Non-limiting examples of suitable non-glass fiberizable inorganic materials include ceramic materials such as silicon carbide, carbon, graphite, mullite, aluminum oxide and piezoelectric ceramic materials. Non-limiting examples of suitable fiberizable organic materials include cotton, cellulose, natural rubber, flax, ramie, hemp, sisal and wool. Non-limiting examples of suitable fiberizable organic polymeric materials include those formed from polyamides (such as nylon and aramids), thermoplastic polyesters (such as polyethylene terephthalate and polybutylene terephthalate), acrylics (such as polyacrylonitriles), polyolefins, polyurethanes and vinyl polymers (such as polyvinyl alcohol). Non-glass fiberizable materials useful in the present invention and methods for preparing and processing such fibers are discussed at length in the Encyclopedia of Polymer Science and Technology, Vol. 6 (1967) at pages 505-712, which is specifically incorporated by reference herein.

[0023] It is understood that blends or copolymers of any of the above materials and combinations of fibers formed from any of the above materials can be used in the present invention, if desired. Moreover, the term strand encompasses at least two different fibers made from differing fiberizable materials. In one non-limiting embodiment of the present invention, the fiber strands contain at least one glass fiber, although they may contain other types of fibers.

[0024] The present invention will now be discussed generally in the context of glass fiber strands, although one skilled in the art would understand that the strand can comprise fibers formed from any fiberizable material known in the art as discussed above. Thus, the discussion that follows in terms of glass fibers applies generally to the other fibers discussed above.

[0025] At least one and preferably all of the fibers of a fiber strand of the present invention have a layer of a forming size composition, preferably a residue of a forming size composition, on at least a portion of the surfaces of the fibers. The layer can be present on portions or on the entire outer surface or periphery of the fibers.

[0026] The aqueous forming size composition of the present invention comprises at least one starch; at least one oil, wax or other lubricant; and selected particles that provide desired properties to the yarn and/or fabric such as, but not limited to, desired interstitial spacing between adjacent fibers and abrasion resistance. The forming size composition can also include at least one film forming material, wetting agent, emulsifying agent, defoamer, humectant, biocide and/or any other conventional material known to those skilled in the art. Non-limiting examples of size compositions are set forth in U.S. Pat. Nos. 5,354,829 and 5,773,146 and K. Loewenstein, The Manufacturing Technology of Continuous Glass Fibres (3d Ed. New York 1983) at page 238-244, which are hereby incorporated by reference.

[0027] Non-limiting examples of starches useful in the present invention include those derived from potatoes, corn, wheat, waxy maize, sago, milo, tapioca or rice. Such starches can have high or low amylose contents and high or low viscosity. The starches of the present invention can be modified by acetylation, chlorination, acid hydrolysis, derivatizing agents, crosslinking agents or enzymatic action, for example. As used herein, the term “high amylose content” means a starch having an amylose content of at least 40 weight percent on a total solids basis, and the term “low amylose content” means a starch having an amylose content of up to 40 weight percent on a total solids basis, and preferably 10 to 40 weight percent. Although not limiting herein, starches having high amylose contents are typically derived from corn starch or hybrid corn starch, whereas starches having a low amylose content can be derived from potato, tapioca or modified corn starches. As used herein, the term “low-viscosity starch” means a starch with a post-cook viscosity of 100 centipoise or less at a temperature of 38° C. (100° F.) and a 6 percent solids level, and the term “high-viscosity starch” means a starch with a post-cook viscosity greater than or equal to 100 centipoise at a temperature of 38° C. (100° F.) and a 6 percent solids level. The viscosity is measured using a No. 61 spindle on a Brookfield Viscometer Model No. DV2+ at about 12 revolutions per minute (rpm). In one non-limiting embodiment of the present invention, the starch component of the forming size composition comprises 50 to 90 weight percent of a high viscosity starch.

[0028] Although not limiting in the present invention, in one embodiment the starch is an “oleophobic starches” which as used herein means those starches which are not compatible with, do not have an affinity for and/or are not capable of dissolving in, yet can be dispersed in, solid predominately hydrocarbon unctuous materials, such as a wax, fat or gelled oil.

[0029] Non-limiting examples of useful oleophobic starches include KOLLOTEX 1250 starch, which is a low viscosity, low amylose potato-based starch etherified with ethylene oxide which is commercially available from AVEBE of the Netherlands: NATIONAL 1554 starch, which is a high viscosity, low amylose crosslinked potato starch; HI-SET 369 starch, which is a low viscosity starch, HYLON and NABOND starches, which are high viscosity starches, each of which are commercially available from National Starch and Chemical Corp. of Bridgewater, N.J.; and AMAIZO 213 starch, which is a high viscosity, crosslinked starch and other AMAIZO starches, which are commercially available from American Maize Products Company of Hammond, Ind. HI-SET 369 is a propylene oxide modified corn starch having an amylose/amylopectin ratio of 55/45.

[0030] Although not limiting in the present invention, in one particular embodiment, the starch is a blend of oleophobic starches, such as but not limited to, a blend of NATIONAL 1554 and AMAIZO 213 starches, or a blend of NATIONAL 1554 and HI-SET 369 starches. In another non-limiting embodiment, a single starch such as, but not limited to KOLLOTEX 1250 starch, is used.

[0031] In one non-limiting embodiment of the present invention, the total percentage of starch in the forming size composition ranges from 10 to 90 weight percent on a total solids basis. In another non-limiting embodiment, the total percentage of starch in the forming size composition ranges from 30 to about 75 weight percent on a total solids basis. In still another non-limiting embodiment, the total percentage of starch in the forming size composition ranges from 40 to 65 weight percent on a total solids basis.

[0032] Although not required, the aqueous forming size composition can also comprises additional film-forming materials. In one non-limiting embodiment of the present invention, the additional film forming materials comprise thermosetting materials, thermoplastic materials, and combinations thereof that form a generally continuous film when applied to the surface of the glass fibers.

[0033] Useful thermosetting materials include, but are not limited to, thermosetting polyesters, epoxy materials, vinyl esters, phenolics, aminoplasts, thermosetting polyurethanes and mixtures thereof. Non-limited examples of suitable thermosetting polyesters include STYPOL polyesters, which are commercially available from Cook Composites and Polymers of Kansas City, Mo., and NEOXIL polyesters, which are commercially available from DSM B.V. of Como, Italy. Useful epoxy materials contain at least one epoxy or oxirane group in the molecule, such as, but not limited to, polyglycidyl ethers of polyhydric alcohols or thiols. Non-limiting examples of suitable epoxy film-forming polymers include EPON® 826 and EPON® 880 epoxy resins, which are commercially available from Shell Chemical Company of Houston, Tex.

[0034] Non-limiting examples of useful thermoplastic polymeric materials include vinyl polymers, thermoplastic polyesters, polyolefins, polyamides (e.g. aliphatic polyamides or aromatic polyamides such as aramid), thermoplastic polyurethanes, acrylic polymers and mixtures thereof. In one non-limiting embodiment of the present invention, vinyl polymers useful in the present invention are N-vinyl amide polymers. In another non-limiting embodiment, the vinyl polymers are polyvinyl pyrrolidones such as PVP K-15, PVP K-30, PVP K-60 and PVP K-90, each of which are commercially available from International Specialty Products Chemicals of Wayne, N.J. Other non-limiting examples of suitable vinyl polymers include RESYN 2828 and RESYN 1037 vinyl acetate copolymer emulsions, which are commercially available from National Starch, and other polyvinyl acetates such as are commercially available from H. B. Fuller and Air Products and Chemicals Co. of Allentown, Pa.

[0035] A non-limiting example of a useful polyvinyl pyrrolidone copolymer is PVPNA S-630 polyvinyl pyrrolidone/vinyl acetate copolymer, which is commercially available from International Specialty Products Chemicals of Wayne, N.J.

[0036] Other thermoplastic polyesters useful in the present invention include, but are not limited to, DESMOPHEN 2000 and DESMOPHEN 2001KS polyesters, both of which are commercially available from Bayer Corp. of Pittsburgh, Pa. Polyesters useful in the present invention include, but are not limited to, RD-847A polyester resin, which is commercially available from Borden Chemicals of Columbus, Ohio, and DYNAKOLL Si 100 chemically modified rosin, which is commercially available from Eka Chemicals AB, Sweden. Useful polyamides include, but are not limited to, the VERSAMID products, which are commercially available from Cognis Corp. of Cincinnati, Ohio, and the EUREDOR products that are available from Ciba Geigy, Belgium. Useful thermoplastic polyurethanes include WITCOBOND® W-290H, which is commercially available from Crompton Corporation of Greenwich, Conn., and RUCOTHANE® 2011L polyurethane latex, which is commercially available from Ruco Polymer Corp. of Hicksville, N.Y.

[0037] The aqueous forming size composition of the present invention can comprise a mixture of one or more thermosetting polymeric materials with one or more thermoplastic polymeric materials.

[0038] The additional film-forming material is present in the aqueous forming size composition in an amount ranging from 0.1 to 30 weight percent on a total solids basis. In one non-limiting embodiment, the additional film-forming material is present in the aqueous forming size composition in an amount ranging from 1 to 10 weight percent on a total solids basis. In another non-limiting embodiment, the additional film-forming material is present in the aqueous forming size composition in an amount ranging from 3 to 8 weight percent on a total solids basis.

[0039] The forming sizing composition of the present invention further comprises one or more, and preferably a plurality of particles that when applied to at least one fiber of the plurality of fibers adhere to the outer surface of the at least one fiber and provide one or more interstitial spaces between adjacent glass fibers of the strand. These interstitial spaces correspond generally to the size of the particles positioned between the adjacent fibers.

[0040] In one non-limiting embodiment of the present invention, the particles are discrete particles. As used herein, the term “discrete” means that the particles do not tend to coalesce or combine to form continuous films under conventional processing conditions, but instead substantially retain their individual distinctness, and generally retain their individual shape or form. The discrete particles of the present invention can undergo shearing, i.e., the removal of a layer or sheet of atoms in a particle, necking, i.e. a second order phase transition between at least two particles, and partial coalescence during conventional fiber processing, and still be considered to be “discrete” particles.

[0041] In one non-limiting embodiment of the present invention, the particles are dimensionally stable. As used herein, the term “dimensionally stable particles” means that the particles will generally maintain their average particle size and shape under conventional fiber processing conditions, such as the forces generated between adjacent fibers during weaving, roving and other processing operations, so as to maintain the desired interstitial spaces between adjacent fibers. In other words, dimensionally stable particles preferably will not crumble, dissolve or substantially deform in the sizing composition to form a particle having a maximum dimension less than its selected average particle size under typical glass fiber processing conditions, such as exposure to temperatures of up to 25° C., preferably up to 100° C., and more preferably up to 140° C. Additionally, the particles should not substantially enlarge or expand in size under glass fiber processing conditions and, more particularly, under composite processing conditions where the processing temperatures can exceed 150° C. As used herein, the phrase “should not substantially enlarge in size” in reference to the particles means that the particles should not expand or increase in size to more than approximately three times their initial size during processing. Furthermore, as used herein, the term “dimensionally stable particles” covers both crystalline and non-crystalline particles.

[0042] In one non-limiting embodiment of the invention, the particles of the sizing compositions are substantially free of heat expandable particles. As used herein, the term “heat expandable particles” means particles filled with or containing a material, which, when exposed to temperatures sufficient to volatilize the material, expand or substantially enlarge in size. These heat expandable particles therefore expand due to a phase change of the material in the particles, e.g., a blowing agent, under normal processing conditions. Consequently, the term “non-heat expandable particle” refers to a particle that does not expand due a phase change of the material in the particle under normal fiber processing conditions, and in one non-limiting embodiment of the present invention, the forming sizing compositions comprise at least one non-heat expandable particle. Generally, the heat expandable particles are hollow particles with a central cavity. In a non-limiting embodiment of the present invention, the cavity can be at least partial filled with a non-solid material such as a gas, liquid, and/or a gel. As used herein, the term “substantially free of heat expandable particles” means less than 50 weight percent of heat expandable particles on a total solids basis, more preferably less than 35 weight percent. In one non-limiting embodiment, the sizing compositions of the present invention are essentially free of heat expandable particles. As used herein, the term “essentially free of heat expandable particles” means the sizing composition comprises less than 20 weight percent of heat expandable particles on a total solids basis, more preferably less than 5 weight percent, and most preferably less than 0.001 weight percent.

[0043] In one non-limiting embodiment of the sizing compositions, the particles are non-waxy. The term “non-waxy” means the materials from which the particles are formed are not wax-like. As used herein, the term “wax-like” means materials composed primarily of unentangled hydrocarbons chains having an average carbon chain length ranging from 25 to 100 carbon atoms^(2,3).

[0044] In another non-limiting embodiment of the present invention, the particles in are discrete, dimensionally stable, non-waxy particles.

[0045] The particles can have any shape or configuration desired. Although not limiting in the present invention, examples of suitable particle shapes include spherical (such as beads, microbeads or hollow spheres), cubic, platy or acicular (elongated or fibrous). Additionally, the particles can have an internal structure that is hollow, porous or void free, or a combination thereof, e.g. a hollow center with porous or solid walls. For more information on suitable particle characteristics see H. Katz et al. (Ed.), Handbook of Fillers and Plastics (1987) at pages 9-10, which are specifically incorporated by reference herein.

[0046] The particles can be formed from materials selected from polymeric inorganic materials, non-polymeric inorganic materials, polymeric organic materials, non-polymeric organic materials, composite materials, and mixtures of any of the foregoing. As used herein, the term “polymeric inorganic material” means a polymeric material having a backbone repeat unit based on an element or elements other than carbon. For more information see J. E. Mark et al. at page 5, which is specifically incorporated by reference herein. As used herein, the term “polymeric organic materials” means synthetic polymeric materials, semisynthetic polymeric materials and natural polymeric materials having a backbone repeat unit based on carbon.

[0047] An “organic material”, as used herein, means carbon containing compounds wherein the carbon is typically bonded to itself and to hydrogen, and often to other elements as well, and excludes binary compounds such as the carbon oxides, the carbides, carbon disulfide, etc.; such ternary compounds as the metallic cyanides, metallic carbonyls, phosgene, carbonyl sulfide, etc.; and carbon-containing ionic compounds such as the metallic carbonates, such as calcium carbonate and sodium carbonate. As used herein, the term “inorganic materials” means any material that is not an organic material. See R. Lewis, Sr., Hawley's Condensed Chemical Dictionary, (12th Ed. 1993) at pages 761-762, and M. Silberberg, Chemistry The Molecular Nature of Matter and Change (1996) at page 586, which are specifically incorporated by reference herein.

[0048] As used herein, the term “composite material” means a combination of two or more differing materials. The particles formed from composite materials generally have a hardness at their surface that is different from the hardness of the internal portions of the particle beneath its surface. More specifically, the surface of the particle can be modified in any manner well known in the art, including, but not limited to, chemically or physically changing its surface characteristics using techniques known in the art, such that the surface hardness of the particle is equal to or less than the hardness of the glass fibers while the hardness of the particle beneath the surface is greater than the hardness of the glass fibers. For example, a particle can be formed from a primary material that is coated, clad or encapsulated with one or more secondary materials to form a composite particle that has a softer surface. In yet another alternative embodiment, particles formed from composite materials can be formed from a primary material that is coated, clad or encapsulated with a different form of the primary material. For more information on particles useful in the present invention, see G. Wypych, Handbook of Fillers, 2nd Ed. (1999) at pages 15-202, which are specifically incorporated by reference herein.

[0049] Representative non-polymeric, inorganic materials useful in forming the particles of the present invention include, but are not limited to, inorganic materials selected from graphite, metals, oxides, carbides, nitrides, borides, sulfides, silicates, carbonates, sulfates and hydroxides. A non-limiting example of a suitable inorganic nitride from which the particles are formed is boron nitride. In one non-limiting embodiment of the particles, the boron nitride particles have a hexagonal crystal structure. A non-limiting example of a useful inorganic oxide is zinc oxide. Suitable inorganic sulfides include, but are not limited to, molybdenum disulfide, tantalum disulfide, tungsten disulfide and zinc sulfide. Useful inorganic silicates include, but are not limited to, aluminum silicates and magnesium silicates, such as vermiculite. Suitable metals include, but are not limited to, molybdenum, platinum, palladium, nickel, aluminum, copper, gold, iron, silver, alloys, and mixtures of any of the foregoing.

[0050] In one non-limiting embodiment of the invention, the particles are formed from solid lubricant materials. As used herein, the term “solid lubricant” means any solid used between two surfaces to provide protection from damage during relative movement and/or to reduce friction and wear. In one non-limiting embodiment, the solid lubricants are inorganic solid lubricants. As used herein, “inorganic solid lubricant” means that the solid lubricants have a characteristic crystalline habit which causes them to shear into thin, flat plates which readily slide over one another and thus produce an antifriction lubricating effect between the fiber surfaces, preferably the glass fiber surface, and an adjacent solid surface, at least one of which is in motion. See R. Lewis, Sr., Hawley's Condensed Chemical Dictionary, (12th Ed. 1993) at page 712, which is specifically incorporated by reference herein. Friction is the resistance to sliding one solid over another. See F. Clauss, Solid Lubricants and Self-Lubricating Solids (1972) at page 1, which is specifically incorporated by reference herein.

[0051] In one non-limiting embodiment of the invention, the particles have a lamellar structure. Particles having a lamellar structure are composed of sheets or plates of atoms in hexagonal array, with strong bonding within the sheet and weak van der Waals bonding between sheets, providing low shear strength between sheets. A non-limiting example of a lamellar structure is a hexagonal crystal structure. See K. Ludema, Friction, Wear, Lubrication (1996) at page 125, Solid Lubricants and Self-Lubricating Solids at pages 19-22, 42-54, 75-77, 80-81, 82, 90-102, 113-120 and 128; and W. Campbell, “Solid Lubricants”, Boundary Lubrication; An Appraisal of World Literature, ASME Research Committee on Lubrication (1969) at pages 202-203, which are specifically incorporated by reference herein. Inorganic solid particles having a lamellar fullerene (buckyball) structure are also useful in the present invention.

[0052] Non-limiting examples of suitable materials having a lamellar structure that are useful in forming the particles of the present invention include boron nitride, graphite, metal dichalcogenides, mica, talc, gypsum, kaolinite, calcite, cadmium iodide, silver sulfide, and mixtures of any of the foregoing. In one non-limiting embodiment of the present invention, the suitable materials include boron nitride, graphite, metal dichalcogenides, and mixtures of any of the foregoing. Suitable metal dichalcogenides include molybdenum disulfide, molybdenum diselenide, tantalum disulfide, tantalum diselenide, tungsten disulfide, tungsten diselenide, and mixtures of any of the foregoing.

[0053] In one non-limiting embodiment, the particles are formed from an inorganic solid lubricant material having a lamellar structure. A non-limiting example of an inorganic solid lubricant material having a lamellar structure for use in the sizing compositions of the present invention is boron nitride, for example boron nitride having a hexagonal crystal structure. Particles formed from boron nitride, zinc sulfide and montmorillonite also provide good whiteness in composites with polymeric matrix materials such as nylon 6,6.

[0054] Non-limiting examples of particles formed from boron nitride that are suitable for use in the present invention are POLARTHERM® 100 Series (PT 120, PT 140, PT 160 and PT 180); 300 Series (PT 350) and 600 Series (PT 620, PT 630, PT 640 and PT 670) boron nitride powder particles, commercially available from Advanced Ceramics Corporation of Lakewood, Ohio. “PolarTherm® Thermally Conductive Fillers for Polymeric Materials”, a technical bulletin of Advanced Ceramics Corporation of Lakewood, Ohio (1996), which is specifically incorporated by reference herein. These particles have a thermal conductivity of 250-300 Watts per meter ° K at 25° C., a dielectric constant of 3.9 and a volume resistivity of 10¹⁵ ohm-centimeters. The 100 Series powder particles have an average particle size ranging from 5 to 14 micrometers, the 300 Series powder particles have an average particle size ranging from 100 to 150 micrometers and the 600 Series powder particles have an average particle size ranging from 16 to greater than 200 micrometers. In particular, as reported by its supplier, POLARTHERM 160 particles have an average particle size of 6 to 12 micrometers, a particle size range of submicrometer to 70 micrometers, and a particle size distribution as follows: % > 10 50 90 Size (μm) 18.4 7.4 0.6

[0055] According to this distribution, ten percent of the POLARTHERM® 160 boron nitride particles that were measured had an average particle size greater than 18.4 micrometers. As used herein, the “average particle size” refers to the mean particle size of the particles.

[0056] The average particle size of the particles according to the present invention can be measured according to known laser scattering techniques. In one non-limiting embodiment of the present invention, the particles size is measured using a Beckman Coulter LS 230 laser diffraction particle size instrument, which uses a laser beam with a wave length of 750 nm to measure the size of the particles and assumes the particle has a spherical shape, i.e. the “particle size” refers to the smallest sphere that will completely enclose the particle. For example, particles of POLARTHERM® 160 boron nitride particles measured using the Beckman Coulter LS 230 particle size analyzer were found to have an average particle size of 11.9 micrometers with particles ranging from submicrometer to 35 micrometers and having the following distribution of particles: % > 10 50 90 Size (μm) 20.6 11.3 4.0

[0057] According to this distribution, ten percent of the POLARTHERM® 160 boron nitride particles that were measured had an average particle size greater than 20.6 micrometers.

[0058] In another non-limiting embodiment of the present invention, the particles are formed from inorganic materials that are non-hydratable. As used herein, “non-hydratable” means that the inorganic particles do not react with molecules of water to form hydrates and do not contain water of hydration or water of crystallization. A “hydrate” is produced by the reaction of molecules of water with a substance in which the H—OH bond is not split. See R. Lewis, Sr., Hawley's Condensed Chemical Dictionary, (12th Ed. 1993) at pages 609-610 and T. Perros, Chemistry, (1967) at pages 186-187, which are specifically incorporated by reference herein. In the formulas of hydrates, the addition of the water molecules is conventionally indicated by a centered dot, e.g., 3MgO•4SiO₂•H₂O (talc), Al₂O₃•2SiO₂•2H₂O (kaolinite). Structurally, hydratable inorganic materials include at least one hydroxyl group within a layer of a crystal lattice (but not including hydroxyl groups in the surface planes of a unit structure or materials which absorb water on their surface planes or by capillary action), for example as shown in the structure of kaolinite given in FIG. 3.8 at page 34 of J. Mitchell, Fundamentals of Soil Behavior (1976) and as shown in the structure of 1:1 and 2:1 layer minerals shown in FIGS. 18 and 19 +L, respectively, of H. van Olphen, Clay Colloid Chemistry, (2d Ed. 1977) at page 62, which are specifically incorporated by reference herein. A “layer” of a crystal lattice is a combination of sheets, which is a combination of planes of atoms. (See Minerals in Soil Environments, Soil Science Society of America (1977) at pages 196-199, which is specifically incorporated by reference herein). The assemblage of a layer and interlayer material (such as cations) is referred to as a unit structure.

[0059] Hydrates contain coordinated water, which coordinates the cations in the hydrated material and cannot be removed without the breakdown of the structure, and/or structural water, which occupies interstices in the structure to add to the electrostatic energy without upsetting the balance of charge. R. Evans, An Introduction to Crystal Chemistry (1948) at page 276, which is specifically incorporated by reference herein. In one non-limiting embodiment of the present invention, the sizing composition is preferably essentially free of hydratable particles. As used herein, the term “essentially free of hydratable particles” means the sizing composition comprises less than 20 weight percent of hydratable particles on a total solids basis, more preferably less than 5 weight percent, and most preferably less than 0.001 weight percent. In one non-limiting embodiment of the present invention, the particles are formed from a non-hydratable, inorganic solid lubricant material.

[0060] The forming size compositions according to the present invention can contain particles formed from hydratable or hydrated inorganic materials in lieu of or in addition to the non-hydratable inorganic materials discussed above. Non-limiting examples of such hydratable inorganic materials are clay mineral phyllosilicates, including micas (such as muscovite), talc, montmorillonite, kaolinite and gypsum.

[0061] In another non-limiting embodiment of the present invention, the particles can be formed from non-polymeric, organic materials. Examples of non-polymeric, organic materials useful in the present invention include, but are not limited to, stearates (such as zinc stearate and aluminum stearate), carbon black and stearamide.

[0062] In yet another non-limiting embodiment of the present invention, the particles can be formed from inorganic polymeric materials. Non-limiting examples of useful inorganic polymeric materials include polyphosphazenes, polysilanes, polysiloxane, polygeremanes, polymeric sulfur, polymeric selenium, silicones, and mixtures of any of the foregoing. A specific non-limiting example of a particle formed from an inorganic polymeric material suitable for use in the present invention is TOSPEARL⁴, which is a particle formed from cross-linked siloxanes and is commercially available from Toshiba Silicones Company, Ltd. of Japan.

[0063] In still another non-limiting embodiment of the present invention, the particles can be formed from synthetic, organic polymeric materials. Suitable organic polymeric materials include, but are not limited to, thermosetting materials and thermoplastic materials. Suitable thermosetting materials include, but are not limited to, thermosetting polyesters, vinyl esters, epoxy materials, phenolics, aminoplasts, thermosetting polyurethanes, and mixtures of any of the foregoing. A non-limiting example of a synthetic polymeric particle formed from an epoxy material is an epoxy microgel particle.

[0064] Suitable thermoplastic materials include, but are not limited to, thermoplastic polyesters, polycarbonates, polyolefins, acrylic polymers, polyamides, thermoplastic polyurethanes, vinyl polymers, and mixtures of any of the foregoing. Suitable thermoplastic polyesters include, but are not limited to, polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate. Suitable polyolefins include, but are not limited to, polyethylene, polypropylene and polyisobutene. Suitable acrylic polymers include, but are not limited to, copolymers of styrene and acrylic monomer and polymers containing methacrylate. Non-limiting examples of synthetic polymeric particles formed from an acrylic copolymer are RHOPLEX® B-85⁵, which is an opaque, non-crosslinking solid acrylic particle emulsion, ROPAQUE® HP-1055⁶, which is an opaque, non-film-forming, styrene acrylic polymeric synthetic pigment having a 1.0 micrometer particle size, a solids content of 26.5 percent by weight and a 55 percent void volume, ROPAQUE® OP-96⁷ and ROPAQUE® HP-543P⁸, which are identical, each being an opaque, non-film-forming, styrene acrylic polymeric synthetic pigment dispersion having a particle size of 0.55 micrometers and a solids content of 30.5 percent by weight, and ROPAQUE® OP-62 LO⁹ which is also an opaque, non-film-forming, styrene acrylic polymeric synthetic pigment dispersion having a particles size of 0.40 micrometers and a solids content of 36.5 percent by weight. Each of these particles is commercially available from Rohm and Haas Company of Philadelphia, Pa.

[0065] The particles according to the present invention can also be formed from semisynthetic, organic polymeric materials and natural polymeric materials. As used herein, a “semisynthetic material” is a chemically modified, naturally occurring material. Suitable semisynthetic, organic polymeric materials from which the particles can be formed include, but are not limited to, cellulosics, such as methylcellulose and cellulose acetate; and modified starches, such as starch acetate and starch hydroxyethyl ethers. Suitable natural polymeric materials from which the particles can be formed include, but are not limited to, polysaccharides, such as starch; polypeptides, such as casein; and natural hydrocarbons, such as natural rubber and gutta percha.

[0066] In one non-limiting embodiment of the present invention, the polymeric particles are formed from hydrophobic polymeric materials to reduce or limit moisture absorption by the coated strand. Non-limiting examples of such hydrophobic polymeric materials include but are not limited to polyethylene, polypropylene, polystyrene and polymethylmethacrylate. Non-limiting examples of polystyrene copolymers include ROPAQUE® HP-1055, ROPAQUE® OP-96, ROPAQUE® HP-543P, and ROPAQUE®OP-62 LO pigments (each discussed above).

[0067] In another non-limiting embodiment of the present invention, polymeric particles are formed from polymeric materials having a glass transition temperature (T_(g)) and/or melting point greater than 25° C. In still another non-limiting embodiment of the present invention, polymeric particles are formed from polymeric materials having a glass transition temperature (T_(g)) and/or melting point preferably greater than 50° C.

[0068] In another non-limiting embodiment of the present invention, the particles can be hollow particles formed from materials selected from polymeric and non-polymeric inorganic materials, polymeric and non-polymeric organic materials, composite materials, and mixtures of any of the foregoing. Non-limiting examples of suitable materials from which the hollow particles can be formed are described above. Non-limiting examples of a hollow polymeric particle useful in present invention are ROPAQUE® HP-1055, ROPAQUE® OP-96, ROPAQUE® HP-543P, and ROPAQUE® OP-62 LO pigments (each discussed above). For other non-limiting examples of hollow particles that can be useful in the present invention see H. Katz et al. (Ed.) (1987) at pages 437-452, which are specifically incorporated by reference herein.

[0069] The particles useful in the forming size composition of present invention can be present in a dispersion, suspension or emulsion in water. Other solvents, such as mineral oil or alcohol (preferably less than 5 weight percent), can be included in the dispersion, suspension or emulsion, if desired. A non-limiting example of a dispersion of particles formed from an inorganic material is ORPAC BORON NITRIDE RELEASECOAT-CONC, which is a dispersion of 25 weight percent boron nitride particles in water and is commercially available from ZYP Coatings, Inc. of Oak Ridge, Tenn. See “ORPAC BORON NITRIDE RELEASECOAT-CONC”, a technical bulletin of ZYP Coatings, Inc., which is specifically incorporated by reference herein. According to this technical bulletin, the boron nitride particles in this product have an average particle size of less than 3 micrometers and include 1 percent of magnesium-aluminum silicate to bind the boron nitride particles to the substrate to which the dispersion is applied. Independent testing of the ORPAC BORON NITRIDE RELEASECOAT-CONC 25 boron nitride using the Beckman Coulter LS 230 particle size analyzer found an average particle size of 6.2 micrometers, with particles ranging from submicrometer to 35 micrometers and having the following distribution of particles: % > 10 50 90 Size (μm) 10.2 5.5 2.4

[0070] According to this distribution, ten percent of the ORPAC BORON NITRIDE RELEASECOAT-CONC 25 boron nitride particles that were measured had an average particle size greater than 10.2 micrometers.

[0071] Other useful products which are commercially available from ZYP Coatings include BORON NITRIDE LUBRICOAT® paint, and BRAZE STOP and WELD RELEASE products. Specific, non-limiting examples of emulsions and dispersions of synthetic polymeric particles formed from acrylic polymers and copolymers include: RHOPLEX® B-85 acrylic emulsion (discussed above), RHOPLEX® GL-623¹⁰ which is an all acrylic firm polymer emulsion having a solids content of 45 percent by weight and a glass transition temperature of 98° C.; EMULSION E-2321¹¹ which is a hard, methacrylate polymer emulsion having a solids content of 45 percent by weight and a glass transition temperature of 105° C.; ROPAQUE® OP-96 and ROPAQUE®) HP-543P (discussed above), which are supplied as a dispersion having a particle size of 0.55 micrometers and a solids content of 30.5 percent by weight; ROPAQUE® OP-62 LO (discussed above), which is supplied as a dispersion having a particles size of 0.40 micrometers and a solids content of 36.5 percent by weight; and ROPAQUE® HP-1055 (discussed above), which is supplied as a dispersion having a solids content of 26.5 percent by weight; all of which are commercially available from Rohm and Haas Company of Philadelphia, Pa.

[0072] In one non-limiting embodiment of the present invention, the sizing composition comprises a mixture of at least one inorganic particle, particularly boron nitride, and more particularly a boron nitride available under the tradename POLARTHERM® and/or ORPAC BORON NITRIDE RELEASECOAT-CONC, and at least one thermoplastic material, particularly a copolymer of styrene and acrylic monomer, and more particularly a copolymer available under the tradename ROPAQUE®.

[0073] The particles are selected to achieve an average particle size sufficient to effect the desired spacing between adjacent fibers. For example, in one non-limiting embodiment of the present invention the average size of the particles incorporated into a forming size composition applied to fibers to be processed on air-jet looms is preferably selected to provide sufficient spacing between at least two adjacent fibers to permit air-jet transport of the fiber strand across the loom. As used herein, “air-jet loom” means a type of loom in which the fill yarn (weft) is inserted into the warp shed by a blast of compressed air from one or more air jet nozzles in a manner well known to those skilled in the art.

[0074] In another non-limiting embodiment, the average size of the particles incorporated into a forming size composition applied to fibers to be impregnated with a polymeric matrix material is selected to provide sufficient spacing between at least two adjacent fibers to permit good wet-out and wet-through of the fiber strand. As used herein, the term “wet-out” means the ability of a material, for example a slashing solution or a polymeric matrix material, to penetrate through the individual bundles or strands of fibers, and the term “wet-through” means the ability of a material, for example a polymeric matrix material, to penetrate through the fabric.

[0075] Although not limiting in the present invention, in one embodiment the particles have an average size, measured using laser scattering techniques, of no greater than 1000 micrometers. In another non-limiting embodiment, the particles have an average size, measured using laser scattering techniques, ranging from 0.001 to 100 micrometers. In another non-limiting embodiment, the particles have an average size, measured using laser scattering techniques, ranging from 0.1 to 25 micrometers.

[0076] In another non-limiting embodiment of the present invention, the average particle size, measured using laser scattering techniques, is at least 0.1 micrometers and in one non-limiting embodiment ranges from 0.1 micrometers to 10 micrometers and in another non-limiting embodiment ranges from 0.1 micrometers to 5 micrometers. In another non-limiting embodiment, the average particle size of the particles, measured using laser scattering techniques, is at least 0.5 micrometers and ranges from 0.5 micrometers to 2 micrometers. In another non-limiting embodiment of the present invention, the particles have an average particle size that is generally smaller than the average diameter of the fibers which the sizing composition is applied. It has been observed that twisted yarns made from fiber strands having a layer of a residue of a forming size composition comprising particles having average particles sizes discussed above can advantageously provide sufficient spacing between adjacent fibers to permit air-jet weavability (i.e., air-jet transport across the loom) while maintaining the integrity of the fiber strand and providing acceptable wet-through and wet-out characteristics when impregnated with a polymeric matrix material.

[0077] In another non-limiting embodiment of the present invention, the average particles size, measured using laser scattering techniques, is at least 3 micrometers and ranges from 3 to 1000 micrometers. In another non-limiting embodiment, the average particle size, measured using laser scattering techniques, is at least 5 micrometers and ranges from 5 to 1000 micrometers. In still another non-limiting embodiment, the particle size ranges from 10 to 25 micrometers, measured using laser scattering techniques. In another non-limiting embodiment, the average particle size corresponds generally to the average nominal diameter of the glass fibers. It has been observed that fabrics made with strands coated with particles falling within the sizes discussed above exhibit good wet-through and wet-out characteristics when impregnated with a polymeric matrix material.

[0078] It will be recognized by one skilled in the art that mixtures of one or more particles having different average particle sizes can be incorporated into the sizing composition in accordance with the present invention to impart the desired properties and processing characteristics to the fiber strands and to the products subsequently made therefrom. More specifically, different sized particles can be combined in appropriate amounts to provide strands having good air-jet transport properties as well to provide a fabric exhibiting good wet-out and wet-through characteristics.

[0079] Fibers are subject to abrasive wear by contact with asperities of adjacent fibers and/or other solid objects or materials which the glass fibers contact during forming and subsequent processing, such as weaving or roving. “Abrasive wear”, as used herein, means scraping or cutting off of bits of the fiber surface or breakage of fibers by frictional contact with particles, edges or entities of materials which are hard enough to produce damage to the fibers. See K. Ludema at page 129, which is specifically incorporated by reference herein. Abrasive wear of fiber strands causes detrimental effects to the fiber strands, such as strand breakage during processing and surface defects in products such as woven cloth and composites, which increases waste and manufacturing cost.

[0080] In the fiber forming step, for example, fibers, particularly glass fibers, contact solid objects such as a metallic gathering shoe and a traverse or spiral before being wound into a forming package. In fabric assembly operations, such as knitting or weaving, the glass fiber strand contacts solid objects such as portions of the fiber assembly apparatus (e.g. a loom or knitting device) which can abrade the surfaces of the contacting glass fibers. Examples of portions of a loom which contact the glass fibers include air jet accumulators and shuttles. Surface asperities of these solid objects that have a hardness value greater than that of the glass fibers can cause abrasive wear of the glass fibers. For example, many portions of the twist frame, loom and knitting device are formed from metallic materials such as steel, which has a Mohs' hardness up to 8.5¹². Abrasive wear of glass fiber strands from contact with asperities of these solid objects causes strand breakage during processing and surface defects in products such as woven cloth and composites, which increases waste and manufacturing cost.

[0081] To minimize abrasive wear, in one non-limiting embodiment of the present invention, the particles have a hardness value which does not exceed, i.e., is less than or equal to, a hardness value of the glass fiber(s). The hardness values of the particles and glass fibers can be determined by any conventional hardness measurement method, such as Vickers or Brinell hardness, but is preferably determined according to the original Mohs' hardness scale which indicates the relative scratch resistance of the surface of a material on a scale of one to ten. The Mohs' hardness value of glass fibers generally ranges from 4.5 to 6.5, and is generally 6. R. Weast (Ed.), Handbook of Chemistry and Physics, CRC Press (1975) at page F-22, which is specifically incorporated by reference herein. As a result, in one non-limiting embodiment of the particles, the Mohs' hardness value of the particles ranges from 0.5 to 6. The Mohs' hardness values of several non-limiting examples of particles formed from inorganic materials suitable for use in the present invention are given in Table A below. TABLE A Particle material Mohs' hardness (original scale) boron nitride 2¹³ graphite 0.5-1¹⁴   molybdenum disulfide 1¹⁵ talc   1-1.5¹⁶ mica 2.8-3.2¹⁷ kaolinite 2.0-2.5¹⁸ gypsum 1.6-2¹⁹   calcite (calcium carbonate) 3²⁰ calcium fluoride 4²¹ zinc oxide 4.5²²   aluminum 2.5²³   copper 2.5-3²⁴   iron 4-5²⁵ gold 2.5-3²⁶   nickel 5²⁷ palladium 4.8²⁸   platinum 4.3²⁹   silver 2.5-4³⁰   zinc sulfide 3.5-4³¹  

[0082] As mentioned above, the Mohs' hardness scale relates to the resistance of a material to scratching. The instant invention therefore further contemplates particles that have a hardness at their surface that is different from the hardness of the internal portions of the particle beneath its surface. More specifically, the surface of the particle can be modified in any manner well known in the art, including, but not limited to, chemically changing the particle's surface characteristics using techniques known in the art such that the surface hardness of the particle is less than or equal to

[0083] the hardness of the glass fibers while the hardness of the particle beneath the surface is greater than the hardness of the glass fibers. As another alternative, a particle can be formed from a primary material that is coated, clad or encapsulated with one or more secondary materials to form a composite material that has a softer surface. Alternatively, a particle can be formed from a primary material that is coated, clad or encapsulated with a differing form of the primary material to form a composite material that has a softer surface.

[0084] In one non-limiting example, an inorganic particle formed from an inorganic material such as silicon carbide or aluminum nitride can be provided with a silica, carbonate or nanoclay coating to form a useful composite particle. In another embodiment, the inorganic particles can be reacted with a coupling agent having functionality capable of covalently bonding to the inorganic particles and functionality capable of crosslinking into the film-forming material or crosslinkable resin. Such coupling agents are described in U.S. Pat. No. 5,853,809 at column 7, line 20 through column 8, line 43, which is incorporated herein by reference. Useful silane coupling agents include glycidyl, isocyanato, amino or carbamyl functional silane coupling agents. In another non-limiting example, a silane coupling agent with alkyl side chains can be reacted with the surface of an inorganic particle formed from an inorganic oxide to provide a useful composite particle having a “softer” surface. Other examples include cladding, encapsulating or coating particles formed from non-polymeric or polymeric materials with differing non-polymeric or polymeric materials. A specific non-limiting example of such composite particles is DUALITE, which is a synthetic polymeric particle coated with calcium carbonate that is commercially available from Pierce and Stevens Corporation of Buffalo, N.Y.

[0085] Although not required, in one non-limiting embodiment of the present invention, the particles are thermally conductive, i.e., preferably have a thermal conductivity of at least 0.2 Watts per meter K, more preferably at least 0.5 Watts per meter K, measured at a temperature of 300 K. In a non-limiting embodiment, the particles have a thermal conductivity of at least 1 Watt per meter K, more preferably at least 5 Watts per meter K, measured at a temperature of 300 K. In another non-limiting embodiment, the thermal conductivity of the particles is at least 25 Watts per meter K, more preferably at least 30 Watts per meter K, and even more preferably at least 100 Watts per meter K, measured at a temperature of 300 K. In another non-limiting embodiment, the thermal conductivity of the particles ranges from 5 to 2000 Watts per meter K, preferably from 25 to 2000 Watts per meter K, more preferably ranges from 30 to 2000 Watts per meter K, and most preferably ranges from 100 to 2000 Watts per meter K, measured at a temperature of 300 K. As used herein, “thermal conductivity” means the property of the particle that describes its ability to transfer heat through itself. See R. Lewis, Sr., Hawley's Condensed Chemical Dictionary, (12th Ed. 1993) at page 305, which is specifically incorporated by reference herein.

[0086] The thermal conductivity of a material can be determined by any method known to one skilled in the art. For example, if the thermal conductivity of the material to be tested ranges from 0.001 Watts per meter K to 100 Watts per meter K, the thermal conductivity of the material can be determined using the preferred guarded hot plate method according to ASTM C-177-85 (which is specifically incorporated by reference herein) at a temperature of 300 K. If the thermal conductivity of the material to be tested ranges from 20 Watts per meter K to 1200 Watts per meter K, the thermal conductivity of the material can be determined using the guarded hot flux sensor method according to ASTM C-518-91 (which is specifically incorporated by reference herein). In other words, the guarded hot plate method is to be used if the thermal conductivity ranges from 0.001 Watts per meter K to 20 Watts per meter K. If the thermal conductivity is over 100 Watts per meter K, the guarded hot flux sensor method is to be used. For ranges from 20 to 100 Watts per meter K, either method can be used.

[0087] In the guarded hot plate method, a guarded hot plate apparatus containing a guarded heating unit, two auxiliary heating plates, two cooling units, edge insulation, a temperature controlled secondary guard, and a temperature sensor read-out system is used to test two essentially identical samples. The samples are placed on either side of the guarded heating unit with the opposite faces of the specimens in contact with the auxiliary heating units. The apparatus is then heated to the desired test temperature and held for a period of time required to achieve thermal steady state. Once the steady state condition is achieved, the heat flow (Q) passing through the samples and the temperature difference (ΔT) across the samples are recorded. The average thermal conductivity (K_(TC)) of the samples is then calculated using the following formula (I):

K _(TC) =QL/A·ΔT  (I)

[0088] wherein L is the average thickness of the samples and A is the average of the combined area of the samples.

[0089] For products incorporating fibers and fabrics comprising selected constituents, e.g. the particles, of the forming size of the present invention, e.g. electronic supports such as printed circuit boards, it is believed that the materials with higher thermal conductivity will more quickly dissipate the heat generated during a drilling operation from the hole area, resulting in prolonged drill tip life. The thermal conductivity of selected material in Table A is included in Table B.

[0090] Although not required, in one non-limiting embodiment of the particles useful in the present invention, the particles are electrically insulative or have high electrical resistivity, i.e., have an electrical resistivity greater than 1000 microohm-cm. Use of particles having high electrical resistivity in the reinforcement for conventional printed circuit board applications as discussed above inhibits loss of electrical signals due to conduction of electrons through the reinforcement. For specialty applications, such as circuit boards for microwave, radio frequency interference and electromagnetic interference applications, particles having high electrical resistivity are not required. The electrical resistance of selected materials in Table A is included in Table B. TABLE B Thermal conductiv- Electrical Mohs' ity (W/m Resistance hardness Inorganic Solid K at (micro ohm- (original Material 300K) centimeters) scale) boron nitride 200³²  1.7 × 10¹⁹ ³³   2³⁴ boron phosphide 350³⁵ — 9.5³⁶ aluminum phosphide 130³⁷ — — aluminum nitride 200³⁸ greater than 10¹⁹ ³⁹   9⁴⁰ gallium nitride 170⁴¹ — — gallium phosphide 100⁴² silicon carbide 270⁴³ 4 × 10⁵ to 1 × 10⁶ ⁴⁴ greater than 9⁴⁵ silicon nitride  30⁴⁶ 10¹⁹ to 10²⁰ ⁴⁷   9⁴⁸ beryllium oxide 240⁴⁹ —   9⁵⁰ zinc oxide  26 — 4.5⁵¹ zinc sulfide  25⁵² 2.7 × 10⁵ to 1.2 × 10¹² ⁵³ 3.5-4⁵⁴ diamond 2300⁵⁵  2.7 × 10⁸ ⁵⁶  10⁵⁷ silicon  84⁵⁸ 10.0⁵⁹    7⁶⁰ graphite up to  100⁶²  0.5-1⁶³ 2000⁶¹  molybdenum 138⁶⁴ 5.2⁶⁵ 5.5⁶⁶ platinum  69⁶⁷ 10.6⁶⁸  4.3⁶⁹ palladium  70⁷⁰ 10.8⁷¹  4.8⁷² tungsten 200⁷³ 5.5⁷⁴ 7.5⁷⁵ nickel  92⁷⁶ 6.8⁷⁷   5⁷⁸ aluminum 205⁷⁹ 4.3⁸⁰ 2.5⁸¹ chromium  66⁸²  20⁸³ 9.0⁸⁴ copper 398⁸⁵ 1.7⁸⁶ 2.5-3⁸⁷ gold 297⁸⁸ 2.2⁸⁹ 2.5-3⁹⁰ iron 74.5⁹¹    9⁹²   4-5⁹³ silver 418⁹⁴ 1.6⁹⁵ 2.5-4⁹⁶

[0091] It will be appreciated by one skilled in the art that particles of the forming size composition of the present invention can include any combination or mixture of particles discussed above. More specifically, and without limiting the present invention, the particles can include any combination of additional particles made from any of the materials described above. Thus, all particles do not have to be the same; they can be chemically different and/or chemically the same but different in configuration or properties.

[0092] Generally, the particles are present in the forming size composition in an amount ranging from 1 to 30 weight percent of the forming size composition on a total solids basis. In one non-limiting embodiment, the particles range from 1 to 20 weight percent of the sizing composition on a total solids basis. In another non-limiting embodiment, the particles range from 1 to 10 weight percent of the sizing composition on a total solids basis. In other non-limiting embodiments of the present

[0093] invention, the forming size compositions include, but are not limited to: i) sizings comprising an organic component and lamellar particles having a thermal conductivity of at least 1 Watt per meter K at a temperature of 300 K; ii) sizings comprising an organic component and non-hydratable, lamellar particles; iii) sizings comprising at least one boron-free lamellar particle having a thermal conductivity of at least 1 Watt per meter K at a temperature of 300 K; iv) lamellar particles having a thermal conductivity of at least 1 Watt per meter K at a temperature of 300 K, i.e., lamellar particles on the fiber; v) alumina-free, non-hydratable particles having a thermal conductivity of at least 1 Watt per meter K at a temperature of 300 K, i.e., alumina-free, non-hydratable particles on the fiber, vi) at least one particle selected from inorganic particles, organic hollow particles and composite particles, the at least one particle having a Mohs' hardness value which does not exceed the Mohs' hardness value of at least one glass fiber, and vii) a plurality of discrete particles formed from materials selected from non-heat expandable organic materials, inorganic polymeric materials, non-heat expandable composite materials and mixtures thereof, the particles having an average particle size sufficient to allow strand wet out without application of external heat.

[0094] The coating compositions of the present invention can further include one or more lubricious materials that are chemically different from the polymeric materials and softening agents discussed above to impart desirable processing characteristics to the fiber strands during weaving. Suitable lubricious materials can be selected from oils, waxes, greases, and mixtures of any of the foregoing. Non-limiting examples of wax materials useful in the present invention include aqueous soluble, emulsifiable or dispersible wax materials such as vegetable, animal, mineral, synthetic or petroleum waxes, e.g. paraffin. Oils useful in the present invention include both natural oils, semisynthetic oils and synthetic oils.

[0095] The lubricious materials can include waxes and oils having polar characteristics such as, but not limited to, highly crystalline waxes having polar characteristics. In one non-limiting embodiment, the waxes has a melting point above 35° C. and in another non-limiting embodiment of the present invention, the waxes have a melting point above 45° C. Such materials are believed to improve the wet-out and wet-through of polar resins on fiber strands coated with sizing compositions containing such polar materials as compared to fiber strands coated with sizing compositions containing waxes and oils that do not have polar characteristics. However, it should be appreciated that the effect such materials have on wet-out and wet-through depends on how much, if any, of these materials remain on the fibers and/or within the fiber strands after heat cleaning. Non-limiting examples of lubricious materials having polar characteristics include esters formed from reacting (1) a monocarboxlyic acid and (2) a monohydric alcohol. Preferably,the wax component comprises at least 90 weight percent of the ester on a total solids basis. Non-limiting examples of such fatty acid esters useful in the present invention include cetyl palmitate (such as is available from Stepan Company of Maywood, N.J. as KESSCO 653 or STEPANTEX 653), cetyl myristate (also available from Stepan Company as STEPANLUBE 654), cetyl laurate, octadecyl laurate, octadecyl myristate, octadecyl palmitate and octadecyl stearate. Other fatty acid ester, lubricious materials useful in the present invention include, but are not limited to, trimethylolpropane tripelargonate, natural spermaceti and triglyceride oils, such as but not limited to soybean oil, linseed oil, epoxidized soybean oil, and epoxidized linseed oil.

[0096] The lubricious materials can also include water-soluble polymeric materials. Non-limiting examples of useful materials include polyalkylene polyols and polyoxyalkylene polyols, such as MACOL E-300, which is commercially available from BASF Corporation of Parsippany, N.J., and CARBOWAX 300 and CARBOWAX 400, which is commercially available from Union Carbide Corporation of Danbury, Conn. Another non-limiting example of a useful lubricious material is POLYOX WSR 301 which is a poly(ethylene oxide) commercially available from Union Carbide Corporation.

[0097] The coating compositions of the present invention can additionally include one or more other lubricious materials, such as non-polar petroleum waxes, in lieu of or in addition to of those lubricious materials discussed above. Non-limiting examples of non-polar petroleum waxes include MICHEM® LUBE 296 microcrystalline wax, POLYMEKON® SPP-W microcrystalline wax and PETROLITE 75 microcrystalline wax which are commercially available from Michelman Inc. of Cincinnati, Ohio and Baker Petrolite, Polymer Division, of Cumming, Ga., respectively.

[0098] Generally, the amount of wax or other lubricious material present in the forming size composition of the present invention ranges from 5 to 50 weight percent of the aqueous sizing composition on a total solids basis. In one non-limiting embodiment, the amount of wax or other lubricious material present in the sizing composition ranges from 20 to 45 weight percent of the aqueous sizing composition on a total solids basis. In another non-limiting embodiment, the amount of wax or other lubricious material present in the sizing composition ranges from 10 to 45 weight percent of the aqueous sizing composition on a total solids basis.

[0099] The forming size compositions of the present invention can additionally include one or more emulsifying agents for emulsifying or dispersing components of the sizing compositions, such as the particles and/or lubricious materials. Non-limiting examples of suitable emulsifying agents or surfactants include polyoxyalkylene block copolymers (such as PLURONICTM F-108 polyoxypropylene-polyoxyethylene copolymer which is commercially available from BASF Corporation of Parsippany, N.J.; PLURONIC F-108 copolymer is available in Europe under the tradename SYNPERONIC F-108), ethoxylated alkyl phenols (such as IGEPAL CA-630 ethoxylated octylphenoxyethanol which is commercially available from GAF Corporation of Wayne, N.J.), polyoxyethylene octylphenyl glycol ethers (such as TRITON X-100, which is commercially available from Union Carbide of Danbury, Conn.), ethylene oxide derivatives of sorbitol esters (such as TMAZ 81 which is commercially available BASF of Parsippany, N.J. and TWEEN 21 and which are commercially available from ICI Americas, Inc. of Atlas Point, Del.), polyoxyethylated vegetable oils (such as ALKAMULS EL-719, which is commercially available from Rhone-Poulenc/Rhodia and EMULPHOR EL-719 which is commercially available from GAF Corp.), ethoxylated alkylphenols (such as MACOL OP-10 SP which is also commercially available from BASF) and nonylphenol surfactants (such as MACOL NP-6 and ICONOL NP-6 which are also commercially available from BASF, and SERMUL EN 668 which is commercially available from CON BEA, Benelux).

[0100] Generally, the amount of emulsifying agent can range from 0.01 to 25 weight percent of the forming size composition on a total solids basis. In one non-limiting embodiment, the amount of emulsifying agent ranges from 0.1 to 10 weight percent of the forming size composition on a total solids basis.

[0101] The aqueous forming size composition can also comprise one or more cationic lubricants different from the lubricious materials discussed earlier. Non-limiting examples of such cationic lubricants are glass fiber lubricants which include amine salts of fatty acids (which can, for example, include a fatty acid moiety having 12 to 22 carbon atoms and/or tertiary amines having alkyl groups of 1 to 22 atoms attached to the nitrogen atom), alkyl imidazoline derivatives (such as can be formed by the reaction of fatty acids with polyalkylene polyamines), acid solubilized fatty acid amides (for example, saturated or unsaturated fatty acid amides having acid groups of 4 to 24 carbon atoms such as stearic amide), acid solubilized polyunsaturated fatty acid amides, condensates of a fatty acid and polyethylene imine and amide substituted polyethylene imines, such as EMERY 6717, a partially amidated polyethylene imine commercially available from Cognis Corporation of Cincinnati, Ohio and ALUBRASPIN 226 which is available from BASF Corp. of Parsippany, N.J.

[0102] Non-limiting examples of useful alkyl imidazoline derivatives are CATION X, which is commercially available from Rhone Poulenc/Rhodia of Princeton, N.J., and ALUBRASPIN 261, which is available from BASF Corp. of Parsippany, N.J.

[0103] Although not limiting in the present invention, in one embodiment the cationic lubricant includes one or more silylated polyamine polymers. One non-limiting example of a cationic lubricant is ALUBRASPIN 227 silylated polyamine polymer lubricant, which is manufactured by BASF Corp. of Parsippany, N.J. and is disclosed in U.S. Pat. No. 5,354,829.

[0104] Generally the amount of cationic lubricant is no greater than 15 weight percent of the forming size composition on a total solids basis. In one non-limiting embodiment, the amount of cationic lubricant ranges from 0.1 to 10 weight percent of the forming size composition on a total solids basis. In another non-limiting embodiment, the amount of cationic lubricant ranges from 1 to 5 weight percent of the forming size composition on a total solids basis.

[0105] The forming size composition can further include one or more surface modifying or coupling agents selected from functional organo silane, organo titanate and organo zirconate coupling agents. Such coupling agents typically have dual functionality. Each metal or silicon atom has attached to it one or more hydrolyzable groups which can react with the glass surface to remove hydroxyl groups and one or more groups which, it is believed, can compatibilize or react with other components in the forming size composition, such as the N-vinyl amide polymer.

[0106] Non-limiting examples of useful functional organo-silane coupling agents include gamma-aminopropyltrialkoxysilanes, gamma-isocyanatopropyltriethoxysilane, vinyl-trialkoxysilanes, glycidoxypropyltrialkoxysilanes and ureidopropyltrialkoxysilanes. Non-limiting examples of useful functional organo-silane coupling agents include A-187 gamma-glycidoxy-propyltrimethoxysilane, A-174 gamma-methacryloxypropyltrimethoxysilane, A-1100 gamma-aminopropyltriethoxysilane silane coupling agents, A-1108 amino silane coupling agent and A-1160 gamma-ureidopropyltriethoxysilane (each of which is commercially available from Crompton Corporation of Greenwich, Conn.). The organo silane coupling agent can be at least partially hydrolyzed with water prior to application to the fibers, for example at a 1:1 stoichiometric ratio or, if desired, applied in unhydrolyzed form. The pH of the water can be modified by the addition of an acid or a base to initiate or speed the hydrolysis of the coupling agent as is well known in the art. Other examples of useful silane coupling agents are set forth in K. Loewenstein, The Manufacturing Technology of Continuous Glass Fibres at page 253 (3d Ed. New York 1983), which is hereby incorporated by reference.

[0107] The amount of coupling agent can range from 0.5 to 25 weight percent of the forming size composition on a total solids basis. In one non-limiting embodiment, the amount of coupling agent ranges from 1 to 10 weight percent of the sizing composition on a total solids basis. In another non-limiting embodiment, the amount of coupling agent ranges from 1 to 5 weight percent of the sizing composition on a total solids basis.

[0108] The aqueous forming size composition can further comprise one or more non-ionic lubricants different from the lubricious materials discussed earlier, which are believed to increase tension in warping. Non-limiting examples of useful non-ionic lubricants include esters of carboxylic acids and polyhydric alcohols, and mineral oils.

[0109] Non-limiting examples of useful non-ionic lubricants include vegetable oils and hydrogenated vegetable oils, such as cottonseed oil, corn oil and soybean oil; trimethylolpropane triesters; pentaerythritol tetraesters; derivatives and mixtures thereof. Useful trimethylolpropane triesters and pentaerythritol tetraesters are commercially available from Stepan Company. The non-ionic lubricants are typically solids or liquids at ambient temperature (about 25° C.).

[0110] One non-limiting non-ionic lubricant is ECLIPSE 102 hydrogenated soybean oil, which is commercially available from Loders Croklaan of Glen Ellyn, Ill.

[0111] The non-ionic lubricant is generally present in the aqueous forming size composition in an amount of 0.001 weight percent to less than 15 weight percent on a total solids basis. In one non-limiting embodiment, the non-ionic lubricant is present in the aqueous forming size composition in an amount ranging from 5 to 15 weight percent on a total solids basis.

[0112] The emulsifying agent can also function as an emulsifier for the non-ionic lubricants, or a second emulsifying agent different from the emulsifying agent for the wax component can be included in the aqueous forming size composition. Any of the emulsifying agents discussed above are also suitable emulsifiers for the non-ionic lubricant.

[0113] The wax component of the forming size composition can also include one or more aqueous soluble, emulsifiable or dispersible waxes different from the ester, which has been described in detail above. Non-limiting examples of such waxes include vegetable, animal, mineral, synthetic or petroleum waxes. In one non-limiting embodiment of the present invention, the wax has a high degree of crystallinity and is obtained from a paraffinic source, such as a microcrystalline wax. Other useful microcrystalline waxes are commercially available from Baker Petrolite, Polymer Division, Cumming, Georgia and Michelman, Inc. of Cincinnati, Ohio. However, in one non-limiting embodiment of the invention, the forming size composition is essentially free of waxes different from the ester. As used herein, “essentially free of waxes different from the ester” means the forming size composition comprises 0.1 to 5 weight percent of the forming size composition on a total solids basis.

[0114] Fungicides, bactericides and anti-foaming materials can also be included in the forming size composition. A non-limiting example of a useful fungicide is methylene-bis-thiocyanate CHEMTREAT CL-2141, which is commercially available from ChemTreat, Inc. of Ashland, Va. A non-limiting example of a suitable bactericide is BIOMET 66 antimicrobial compound, which is commercially available from M & T Chemicals of Rahway, N.J. Non-limiting examples of suitable anti-foaming materials are the SAG materials, which are commercially available from Crompton Corporation of Greenwich, Conn., and Mazu DF-136, which is commercially available from BASF Corp. of Parsippany, N.J.

[0115] The amount of fungicide, bactericide or anti-foaming materials generally ranges from 1×10⁻⁴ to 5 weight percent of the forming size composition on a total solids basis.

[0116] The forming size composition can further comprise one or more organic acids in an amount sufficient to provide the aqueous forming size composition with a pH ranging from 3 to 10. In one non-limiting embodiment of the present invention, the forming size composition comprises one or more organic acids in an amount sufficient to provide the aqueous forming size composition with a pH ranging from 4 to 8. Non-limiting examples of organic acids suitable for use in the present invention include mono- and polycarboxylic acids and/or anhydrides thereof, such as acetic, citric, formic, propionic, caproic, lactic, benzoic, pyruvic, oxalic, maleic, fumaric, acrylic, methacrylic acids and mixtures thereof.

[0117] Water (preferably deionized) is the predominant solvent for the forming size composition and is present in an amount sufficient to facilitate application of a generally uniform coating upon the glass fibers. The weight percentage of solids of such an aqueous forming size composition can range from 0.5 to 20 weight percent. In one non-limiting embodiment of the present invention, the weight percentage of solids ranges from 1 to 10 weight percent. In another non-limiting embodiment of the present invention, the weight percentage of solids ranges from 2 to 8 weight percent.

[0118] The aqueous forming size composition can further include one or more humectants. Non-limiting examples of humectants include dihydric alcohols, polyhydric alcohols, ureas and mixtures thereof. Non-limiting examples of polyhydric alcohols include polyalkylene polyols, polyoxyalkylene polyols and mixtures thereof. Non-limiting examples of such humectants include polyethylene glycols, such as MACOL E-300, which is commercially available from BASF Corp. of Parsippany, N.J. and CARBOWAX products, which are commercially available from Union Carbide Corp. of Danbury, Conn. Other humectants include glycerols such as are commercially available from Sigma Chemical and Dow Chemical USA of Midland, Mich. However, in one non-limiting embodiment of the invention, the size composition is essentially free of humectants. As used herein, “essentially free of humectants” means that the aqueous forming size composition contains less than 5 weight percent of humectants based upon the total weight of the composition, and preferably less than about 3 weight percent.

[0119] Without limiting the present invention, in one embodiment, the aqueous forming size composition is essentially free of polyolefin emulsions, such as aqueous emulsions of polyolefins selected from polyethylene, polypropylene and copolymers of ethylene and propylene. Such polyolefin emulsions are believed to be hydrophobic and are believed to adversely affect wet-out in slashing, particularly under humid conditions or when water-based slashing sizes are used. A non-limiting example of a high density polyethylene emulsion is PROTOLUBE HD, which is commercially available from Sybron Chemicals of Birmingham, N.J. As used herein, “essentially free of polyolefin emulsions” means that the aqueous forming size composition contains less than 5 weight percent of polyolefin emulsions based upon the total weight of the sizing composition.

[0120] Without limiting the present invention, in one embodiment the aqueous forming size composition is essentially free of preservatives selected from organometallic compounds, formaldehydes, derivatives and mixtures thereof. Non-limiting examples of such preservatives include emulsified organotin compounds and formalin. As used herein, “essentially free of preservatives selected from organometallic compounds, formaldehydes, derivatives and mixtures thereof” means that the aqueous forming size composition contains less than 0.01 weight percent of such preservatives on a total solids basis.

[0121] Without limiting the present invention, in one embodiment the aqueous forming size composition is essentially free of salts of polyamino functional polyamide resins, such as are obtained by the condensation of a polyamine with a difunctional fatty acid. Such salts of polyamino functional polyamide resins are believed to increase resistance to heat cleaning, cause darkening or discoloration the cloth in heat cleaning and produce slashing problems. Such polyamines can include alkyl amines having 2 to 8 carbon atoms. Such difunctional fatty acids include those obtained from the dimerization of fatty acids having 8 to 18 carbons atoms. Non-limiting examples of salts of polyamino functional polyamide resins include the VERSAMID and GENAMID products, which are commercially available from Cognis Corp. of Cincinnati, Ohio and EPICURE 3180 E-75 polyamide resin solution, which is commercially available from Shell Chemical of Houston, Tex. The phrase “essentially free of salts of polyamino functional polyamide resins” means that the aqueous forming size composition comprises less than 4 weight percent, and more preferably less than 1 weight percent, of salts of polyamino functional polyamide resins on a total solids basis.

[0122] As discussed earlier, the heat cleaning operation can remove portions of the forming size composition from the fibers of a fabric. In one non-limiting embodiemnt of the present invention, it is anticipated that at least a portion of the particles as disclosed herein will remain on the surface of the fibers and/or within the fiber bundles after heat cleaning so that the particles can provide protection to the fibers during subsequent processing. In another non-limiting embodiment of the present invention, it is anticipated that at least a portion of the particles as disclosed herein, will remain on the surface of the fibers and/or within the fiber bundles after heat cleaning and are compatible with a resin applied the the fabric and facilitate good penetration of the resin when applied to the fiber strand bundles. In addition, since the particles thereafter become part of the fiber/resin composite, the particles can provide additional properties to the composite such as but not limited to improved drilling properties, desired thermal conductivity and electrical resistivity, as discussed earler. It is also anticipated that other selected constituents of the forming size may also remain on the surface of the fibers and/or within the fiber bundles after heat cleaning and may provide the additional properties to the fabric and/or composite as discussed earlier.

[0123] The aqueous forming size composition of the present invention can be prepared by any suitable method well known to those of ordinary skill in the art.

[0124] As discussed earlier, the forming size compositions of the present invention can be applied to any type of fiberizable glass composition known to those skilled in the art In addition, the aqueous forming size compositions can be applied to the glass fibers in a variety of conventional ways, for example, by dipping the glass fibers in a bath containing the composition, by spraying the composition upon the glass fibers or by contacting the glass fibers with an applicator such as a roller or belt applicator. In one non-limiting embodiment of applying the size composition, the aqueous forming size composition is applied by a belt or roller applicator. Non-limiting examples of such applicators and other suitable applicators are disclosed in Loewenstein at pages 169-177, which is hereby incorporated by reference.

[0125] The amount of the forming size composition applied to the glass fibers can vary based upon such factors as the size and number of glass fibers. For a plurality of glass fibers, the amount of aqueous forming size composition having 0.5 to 20 weight percent solids applied to the fibers ranges from 0.1 to 40 weight percent of the total weight of the glass fibers including the forming size composition. In one non-limiting embodiment, the amount of aqueous forming size composition ranges from 1 to 20 weight percent of the total weight of the glass fibers including the forming size composition.

[0126] After application of the forming size composition to the glass fibers, the glass fibers are typically dried, for example air dried or dried in a conventional or vacuum oven to produce glass fiber strands having a dried residue of the forming size composition thereon. Suitable ovens for drying glass fibers are well known to those skilled in the art. The temperature and time for drying the glass fibers will depend upon such variables as the percentage of solids in the forming size composition, components of the forming size composition and type of glass fiber. A typical, although non-limiting drying cycle includes heating the fibers to a temperature range of 104° C. to 149° C. (220° F. to 300° F.) for 10 to 13 hours. Drying of glass fiber forming packages, or cakes, is discussed in detail in Loewenstein at pages 224-230, which is hereby incorporated by reference.

[0127] Although not limiting in the present invention, the amount of solids of the forming size composition of the present invention on the fiber strands as measured by loss on ignition (LOI), typically ranges from 0.01 to 8 weight percent. In one non-limiting embodiment of the invention, the LOI ranges from 0.2 to 3 weight percent. As used herein the term “loss on ignition” means the weight percent of dried coating composition present on the surface of the fiber strand as determined by the following formula (II):

LOI=100×[(W _(dry)-W _(bare))/W _(dry)]  (II)

[0128] wherein W_(dry) is the weight of the fiber strand plus the residue of the coating composition after drying in an oven at 220° F. (104° C.) for 60 minutes and W_(bare) is the weight of the bare fiber strand after removal of residue of the coating composition by heating the fiber strand in an oven at 1150° F. (621° C.) for 20 minutes and cooling to room temperature in a dessicator.

[0129] Glass fiber strands having the dried forming size composition of the present invention applied thereto can be used, for example, as a warp strand and/or weft strand of a woven fabric, as discussed earlier. In addition, the glass fibers can be twisted and/or can have applied thereon a secondary treatment or coating composition. For example, for glass fiber strands used in the weaving process, a slashing composition is typically applied to the sized glass fiber during warping or beaming. Such slashing compositions typically include components such as polyvinyl alcohol and are well known to those skilled in the art. The slashing operation is used to protect the warp yarn from abrasion as fill yarn is inserted between the warp yarns in a weaving operation. As discussed earlier, the particles of the present invention provide desired interstitial spacing between the fibers. As a result, the forming size of the present invention can facilitate penetration of the fiber strands by the slasing size. However, also as discussed earlier, the particles included in the forming size of the present invention can act as lubricants that reduce the abrasive wear on the warp yarn. As a result, the forming size of the present invention may reduce or possibly eliminate the need for applying a slashing size to the warp yarn prior to weaving.

[0130] The secondary treatment or coating composition can also be an impregnating composition such as are disclosed in Loewenstein at page 253, which is hereby incorporated by reference, and U.S. Pat. Nos. 4,762,750 (col. 5, line 58 through col. 15, line 64; col. 17, lines 16-46; and col. 19, line 28 through col. 26) and 4,762,751, (col. 6, line 21 through col. 14, line 68 and col. 16, line 49 through col. 25, line 23) which are hereby incorporated by reference or a Teflon® polytetrafluoroethylene coating, for example.

[0131] The glass fiber strands can be further processed by twisting into a yarn, chopping, combination in parallel to form a bundle or roving, weaving into a cloth or forming into a chopped or continuous strand mat, as discussed above. The glass fiber strands can be twisted by any conventional twisting technique known to those skilled in the art, for example by using twist frames. Generally, twist is imparted to the strand by feeding the strand to a bobbin rotating at a speed which would enable the strand to be wound onto the bobbin at a faster rate than the rate at which the strand is supplied to the bobbin. Generally, the strand is threaded through an eye located on a ring which traverses the length of the bobbin to impart twist to the strand, typically about 0.5 to about 3 turns per inch.

[0132] Twisted strands and non-twisted strands (sometimes referred to as zero twist strands) can be used to prepare woven or non-woven fabrics, knitted or braided products, or reinforcements. A suitable woven reinforcing fabric can be formed by using any conventional loom well known to those skilled in the art, such as a shuttle loom or rapier loom, but preferably is formed using an air jet loom. Air jet looms are commercially available, for example, from Tsudakoma of Japan as Model No. 103 and Sulzer Brothers Ltd. of Zurich, Switzerland as Model Nos. L-5000 or L-5100. See Sulzer Ruti L5000 and L5100 Product Bulletins of Sulzer Ruti Ltd., Switzerland, which are hereby incorporated by reference. As used herein, “air jet weaving” means a type of fabric weaving using an air jet loom in which fill yarn (weft) is inserted into a warp shed formed by the warp yarn by a blast of compressed air from one or more air jet nozzles, in a manner well known to those skilled in the art. The fill yarn is propelled across the width of the fabric, typically 10 to 60 inches (0.254 to 1.524 meters), by the compressed air.

[0133] The compatibility and aerodynamic properties of different yarns with the air jet weaving process can be determined by the following method, which will generally be referred to herein as the “Air Jet Transport Drag Force” Test Method. The Air Jet Transport Drag Force Test is used to measure the attractive or pulling force (“drag force”) exerted upon the yarn as the yarn is pulled into the air jet nozzle by the force of the air jet. In this method, each yarn sample is fed at a rate of about 274 meters (about 300 yards) per minute through a Sulzer Ruti needle air jet nozzle unit Model No. 044 455 001 which has an internal air jet chamber having a diameter of 2 millimeters and a nozzle exit tube having a length of 20 centimeters (commercially available from Sulzer Ruti of Spartanburg, N.C.) at a desired air pressure, typically between about 172 to about 379 kiloPascals (about 25 to about 55 pounds per square inch) gauge. A tensiometer is positioned in contact with the yarn at a position prior to the yarn entering the air jet nozzle. The tensiometer provides a measurement of the gram force (drag force) exerted upon the yarn by the air jet as the yarn is pulled into the air jet nozzle.

[0134] The drag force per unit mass can be used as a basis for relative comparison of yarn samples. For relative comparison, the drag force measurements are normalized over a one centimeter length of yarn. The Gram Mass of a one centimeter length of yarn can be determined according to the following formula (III):

Gram Mass=(π(d/2)²) (N) (ρ_(glass)) (1 centimeter length of yarn)  (III)

[0135] where d is the diameter of a single fiber of the yarn bundle, N is the number of fibers in the yarn bundle and ρ_(glass) is the density of the glass at a temperature of 25° C. (2.6 grams per cubic centimeter). Table C lists the diameters and number of fibers in a yarn for several typical glass fiber yarn products. TABLE C Fiber Diameter Yarn type (centimeters) Number of Fibers in Bundle G75 9 × 10⁻⁴ 400 G150 9 × 10⁻⁴ 200 E225 7 × 10⁻⁴ 200 D450 5.72 × 10⁻⁴   200 DE75 6.35 × 10⁻⁴   800

[0136] For example, the Gram Mass of a one centimeter length of G75 yarn is (π(9×10⁻⁴/2)²)(400)(2.6 grams per cubic centimeter)(1 centimeter length of yarn)=6.62×10⁻⁴ gram mass. For DE75 yarn, the Gram Mass is 6.59×10⁻⁴ gram mass. The relative drag force per unit mass (“Air Jet Transport Drag Force”) is calculated by dividing the drag force measurement (gram force) determined by the tensiometer by the Gram Mass for the type of yarn tested. For example, for a sample of G75 yarn, if the tensiometer measurement of the drag force is 68.5, then the Air Jet Transport Drag Force is equal to 68.5 divided by 6.62×10⁻⁴=103,474 gram force per gram mass of yarn.

[0137] The forming size coated strands can be used in a wide variety of applications, such as cloth for printed circuit boards and overwrap reinforcements for optical fiber cables, for example.

[0138] The present invention will now be illustrated by the following specific, non-limiting example.

EXAMPLES

[0139] Each of the components in the amounts (weight percent of total solids) set forth in Tables 1, 2 and 3 were mixed to form aqueous sizing compositions useful in the present invention. TABLE I Wt. Percent Component on Total Solids Basis Sample Component 1 2 NATIONAL 1554⁹⁷ 25.7 23.9 AMAIZO 213⁹⁸ 26.5 24.7 CT 7000⁹⁹ 33.1 30.8 TMAZ 81¹⁰⁰ 3.8 3.5 MACOL OP-10 SP¹⁰¹ 1.4 1.3 POLARTHERM PT 160¹⁰² 0.9 3.0 RELEASECOAT-CONC 25¹⁰³ 2.0 6.7 ALUBRASPIN 261¹⁰⁴ 2.2 2.0 EPICURE 3180 E-75¹⁰⁵ 1.0 0.9 MAZU DF 136¹⁰⁶ 0.8 0.8 Y-5659¹⁰⁷ 2.6 2.4 CL-2141¹⁰⁸ <0.1 <0.1 acetic acid¹⁰⁹ <0.1 <0.1 est. % solids in sizing 6.7 7.2 LOI 0.99 0.99

[0140] TABLE 2 Wt. Percent Component on Total Solids Basis Sample Component 3 4 5 6 7 8 NATIONAL 1554 ¹¹⁰ 48.5 45.4 45.3 44.8 44.1 39.8 AMAIZO 213 ¹¹¹ 8.8 8.3 8.3 8.2 8.0 7.2 DGS ¹¹² 1.2 1.1 1.1 1.1 1.1 1.0 ECLIPSE 102 ¹¹³ 23.0 21.5 21.5 21.3 21.0 18.9 TWEEN 81 ¹¹⁴ 3.3 3.1 3.1 3.0 3.0 2.7 POLARTHERM PT 160 ¹¹⁵ — — — — 1.2 2.4 CATION X ¹¹⁶ 3.2 3.0 3.0 3.0 2.9 2.6 CARBOWAX 300 ¹¹⁷ 12.0 11.2 11.2 11.1 10.9 9.8 RELEASECOAT-CONC — — — — 0.8 1.6 25 ¹¹⁸ CL-2141 ¹¹⁹ <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 RHOPLEX B-85 ¹²⁰ — 6.4 — — — — ROPAQUE HP-1055 ¹²¹ — — 6.5 — — — ROPAQUE HP-543P ¹²² — — — 7.5 — — ROPAQUE OP-96 ¹²³ — — — — 7.0 14.0 est. % solids in sizing 6.3 6.7 6.7 6.8 6.9 7.7

[0141] TABLE 3 Wt. Percent Component on Total Solids Basis Sample Component 9 10 11 12 13 14 NATIONAL 1554 ¹²⁴ 23.8 21.8 21.9 21.8 21.6 19.5 AMAIZO 213 ¹²⁵ 24.5 22.5 22.5 22.5 22.2 20.1 KESSCO 653 ¹²⁶ 27.2 25.1 25.1 25.1 24.8 22.4 ECLIPSE 102 ¹²⁷ 11.7 10.7 10.8 10.7 10.6 9.6 TWEEN 81 ¹²⁸ 4.0 3.7 3.7 3.7 3.7 3.3 IGEPAL CA-630 ¹²⁹ 1.4 1.3 1.3 1.4 1.3 1.1 POLARTHERM PT 160 ¹³⁰ — — — 1.2 2.4 PVP K-30 ¹³¹ 4.8 4.4 4.4 4.4 4.4 3.9 ALUBRASPIN 227 ¹³² 2.6 2.4 2.4 2.4 2.4 2.1 RELEASECOAT-CONC — — — 0.8 1.6 25 ¹³³ CL-2141 ¹³⁴ <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 RHOPLEX B-85 ¹³⁵ — 8.1 — — — — ROPAQUE HP-1055 ¹³⁶ — — 7.9 — — ROPAQUE HP-543P ¹³⁷ — — — 8.0 — — ROPAQUE OP-96 ¹³⁸ 7.0 14.0 acetic acid ¹³⁹ <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 est. % solids in sizing 4.9 5.4 5.3 5.3 5.4 6.0

[0142] Samples 1 and 2 in Table 1 were prepared as follows:

[0143] 1. NATIONAL 1554 and AMAIZO 213 were combined with water (preferably deionized) at a temperature ranging from 10° C. to 40° C. in a premix slurry tank; the materials were then mixed until the starch was dispersed; the starch was then cooked in a cooker, such as a standard jet cooker, at a temperature of 124° C. (255° F.), and then transfered to a main mix tank for subsequent processing.

[0144] 2. In a seperate vessel, CT 7000, TMAZ 81, MACOL OP-10 SP and POLARTHERM PT 160 were combined with hot water to melt the materials; the materials were then mixed in a high shear mixer; additional hot water was added until there was an inversion; the materials were then added to the main tank.

[0145] 3. RELEASECOAT-CONC 25 was then added to the main tank.

[0146] 4. In a seperate vessel, ALUBRASPIN 261 was mixed with water to melt it; the materials were then added to the main mix tank.

[0147] 5. In a seperate vessel, EPICURE 3180-F-75 were combined with water and about half of the acetic acid; materials were then added to the tank.

[0148] 6. MAZU DF 136 was then added to the main tank

[0149] 7. In a seperate vessel, Y-5659 was combined with water and the remaining portion of the acetic acid; the materials were then added to the main tank.

[0150] 8. CL-2141 was then added to the main tank.

[0151] 9. Water was then added, as required, to dilute to the required volume.

[0152] Samples 3-6 in Table 2 were prepared as follows:

[0153] 1. NATIONAL 1554 and AMAIZO 213 were combined with water (preferably deionized) at a temperature ranging from 10° C. to 40° C. in a premix slurry tank; the materials were then mixed until the starch was dispersed; the starch was then cooked in a cooker, such as a standard jet cooker, at a temperature of 124° C. (255° F.), and then transfered to a main mix tank for subsequent processing.

[0154] 2. In a seperate vessel, ECLIPSE 102 was melted with hot water; DGS TWEEN 81, and POLARTHERM PT 160 were added and melted, as required; the materials were then emulsified in a high shear mixer and added to the main mix tank.

[0155] 3. CATION X was then added to the main tank.

[0156] 4. CARBOWAX 300 was then added to the main tank.

[0157] 5. RELEASECOAT-CONC 25 was then added to the main tank.

[0158] 6. CL-2141 was then added to the main tank.

[0159] 7. RHOPLEX B-85/ROPAQUE HP-1055/ROPAQUE HP-543P were then added to the main tank.

[0160] 8. Water was then added, as required, to dilute to the required volume.

[0161] Samples 9 and 12 in Table 3 were prepared as follows:

[0162] 1. NATIONAL 1554 and AMAIZO 213 were combined with water (preferably deionized) at a temperature ranging from 10° C. to 40° C. in a premix slurry tank; the materials were then mixed until the starch was dispersed; the starch was then cooked in a cooker, such as a standard jet cooker, at a temperature of 124° C. (255° F.), and then transfered to a main mix tank for subsequent processing.

[0163] 2. In a separate vessel, KESSCO 653 and ECLIPSE 102 were melted with hot water; TWEEN 81, IGEPAL CA-630, and POLARTHERM PT 160 were added and melted, as required; the materials were then emulsified in a high shear mixer and added to the main mix tank.

[0164] 3. PVP K-30 was then added to the main tank.

[0165] 4. In a separate vessel, ALUBRASPIN 227 was mixed with acetic acid and added to the main mix tank.

[0166] 5. RELEASECOAT-CONC 25 was then added to the main tank.

[0167] 6. CL-2141 was then added to the main tank.

[0168] 7. RHOPLEX B-85/ROPAQUE HP-1055/ROPAQUE HP-543P was then added to the main tank.

[0169] 8. Water was then added, as required, to dilute to the required volume.

[0170] Samples 1 and 2 were applied to G75 E-glass fiber strands that were subsequently dried, twisted and woven into a 7623 style fabric. The LOI is indicated in Table 1. No testing of the fabric was conducted.

[0171] Samples 3-6 and 9-12 were applied to DE75 E-glass fiber strands. Each coated glass fiber strand was twisted at 0.7 turns per inch to form a yarn and wound onto 2 bobbins in a similar manner using conventional twisting equipment. Each bobbin of Samples 3-6 and 9-12 had loss on ignition value as shown in Table 4. Samples 3-6 and 9-12 were tested as discussed below.

[0172] Samples 7 and 8 in Table 2 and Samples 13 and 14 in Table 3 are hypothetical sizing formulations that include both boron nitride particles and acrylic copolymer particles. No fiber strands coated with these sizing formulations were produced.

TEST 1

[0173] The yarns of Samples 3-6 and 9-12 were evaluated for Friction Force by pulling each yarn Sample at a rate of 262 meters (287 yards) per minute through a pair of conventional electronic tensiometers and around a stationary stainless steel cylinder with a 4.445 centimeters (1.75 inches) diameter aligned between the tensiometers such that the yarn Samples made one complete wrap around the cylinder. The difference in tension between the tensiometers (in grams) as set forth in Table 4 below is a measure of the friction against the metal surface and is intended to be similar to the frictional forces to which the yarn may be subjected during weaving operations. TABLE 4 Friction Friction Friction Friction Force Force Force Force LOI (grams) LOI (grams) LOI (grams) LOI (grams) Samples 3 4 5 6 Bobbin 1 1.33 42.62 1.62 41.87 1.52 37.37 1.53 48.14 Bobbin 2 1.55 37.46 1.34 43.56 1.41 46.11 1.57 48.42 Samples 9 10 11 12 Bobbin 1 1.17 40.41 1.55 47.59 1.62 48.37 1.45 39.77 Bobbin 2 1.10 40.22 1.46 47.49 1.32 42.63 1.37 40.49

[0174] As shown in Table 4, Samples 4-6 and 10-12, which were coated with starch-oil based sizing compositions containing acrylic copolymer particles of the present invention, had comparable friction force to Samples 3 and 9, respectively.

TEST 2

[0175] The compatibility of the DE75 sample yarns with the air jet weaving process were determined using the “Air Jet Transport Drag Force” Test Method discussed in detail above.

[0176] Each yarn sample was fed at a rate of 274 meters (300 yards) per minute through a Sulzer Ruti needle air jet nozzle unit Model No. 044 455 001 which had an internal air jet chamber having a diameter of 2 millimeters and a nozzle exit tube having a length of 20 centimeters (commercially available from Sulzer Ruti of Spartanburg, N.C.) at an air pressure varying from 25 to 55 pounds per square inch (172 to 379 310 kiloPascals) gauge. A tensiometer was positioned in contact with the yarn at a position prior to the yarn entering the air jet nozzle. The tensiometer provided measurements of the gram force (drag force) exerted upon each yarn sample by the air jet as the respective yarn sample was pulled into the air jet nozzle. These values are set forth in Table 5 below. TABLE 5 Samples 3 4 5 6 9 10 11 12 Air Pressure Drag Force (grams)* 25 psi Bobbin 1 57.68 49.82 52.03 50.87 47.46 49.27 53.98 50.21 Bobbin 2 48.42 51.63 55.43 51.34 50.42 48.97 51.16 51.36 30 psi Bobbin 1 70.90 63.47 62.74 66.11 60.11 63.77 70.45 63.47 Bobbin 2 64.50 68.62 70.61 66.16 63.04 64.51 66.34 67.07 35 psi Bobbin 1 87.97 79.26 79.68 79.44 73.17 76.93 85.37 75.83 Bobbin 2 79.03 80.91 84.22 81.96 76.48 79.01 80.27 81.96 40 psi Bobbin 1 100.74 94.62 90.54 93.92 82.92 91.03 100.49 89.96 Bobbin 2 92.48 96.51 98.85 95.67 86.80 93.04 95.21 94.48 45 psi Bobbin 1 109.79 100.63 103.18 101.95 89.75 98.84 108.24 99.60 Bobbin 2 101.93 102.61 106.08 105.34 95.21 99.98 103.32 103.73 50 psi Bobbin 1 122.13 116.25 110.10 114.60 100.68 110.80 117.20 109.71 Bobbin 2 113.72 114.62 119.93 117.95 107.51 114.74 115.19 113.62 55 psi Bobbin 1 136.54 123.64 127.65 126.27 115.65 123.32 131.04 124.30 Bobbin 2 129.46 128.19 132.51 131.09 118.27 127.21 127.05 126.36

[0177] As shown in Table 5 above, each of the yarns coated with a starch-oil based sizing composition that included the acrylic copolymer particle according to the present invention had a drag force comparable to that of the corresponding commercially available starch-oil based sizings.

[0178] From the foregoing, it is expected that glass fiber yarns coated with an aqueous forming size composition as disclosed herein provide weaving processing at least comparable to yarn coated with conventional starch-oil sizings that do not include the particles as disclosed herein.

[0179] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications which are within the spirit and scope of the invention, as defined by the appended claims. 

Therefore, we claim:
 1. A coated fiber strand comprising at least one fiber having a residue of an aqueous forming size composition applied to at least a portion of a surface of the at least one fiber, the aqueous forming size composition comprising: (a) at least one starch; (b) at least one film-forming material; (c) at least one lubricant; and (d) a plurality of discrete particles that provide interstitial space between the at least one fiber and at least one adjacent fiber sufficient to allow wet out of the fiber strand.
 2. The fiber strand according to claim 1, wherein the at least one starch is present in the aqueous forming size composition in an amount ranging from 10 to 90 weight percent on a total solids basis.
 3. The fiber strand according to claim 2, wherein the at least one starch is an oleophobic starch.
 4. The fiber strand according to claim 1, wherein the at least one film forming material is present in the aqueous forming size composition in an amount ranging from 0.1 to 30 weight percent on a total solids basis.
 5. The fiber strand according to claim 4, wherein the at least one film forming material is selected from thermosetting materials and thermoplastic materials.
 6. The fiber strand according to claim 5, wherein the at least one film forming material comprises a n-vinyl amide polymer.
 7. The fiber strand according to claim 1, wherein the at least one lubricant is present in the aqueous forming size composition in an amount ranging from 5 to 50 weight percent of the aqueous forming size composition on a total solids basis.
 8. The fiber strand according to claim 7, wherein the at least one lubricant comprises a highly crystalline wax having a polar characteristic.
 9. The fiber strand according to claim 7, wherein the at least one lubricant is selected from cetyl palmitate, cetyl myristate, cetyl laurate, octadecyl laurate, octadecyl myristate, octadecyl palmitate, octadecyl stearate, trimethylolpropane tripelargonate, natural spermaceti and triglyceride oils.
 10. The fiber strand according to claim 8, wherein the forming size composition further comprises at least one emulsifying agent present in an amount ranging from 0.1 to 10 weight percent of the forming size composition on a tolid solids basis; and at least one cationic lubricant different from the at least one highly crystalline wax present in an amount ranging from 0.01 to 15 weight percent of the forming size composition on a total solids basis.
 11. The fiber strand according to claim 10, wherein the at least one starch comprises an oleophobic starch; the at least one film-forming material comprises a N-vinyl amide polymer; and the at least one lubricant comprises an ester.
 12. The fiber strand according to claim 1, wherein the at least one fiber comprises at least one inorganic fiber comprising a glass material selected from E-glass, D-glass, S-glass, Q-glass, E-glass derivatives and combinations thereof.
 13. The fiber strand according to claim 1, wherein the particles are dimensionally stable selected from polymeric organic materials, non-polymeric organic materials, polymeric inorganic materials, non-polymeric inorganic materials, composite materials and mixtures thereof.
 14. The fiber strand according to claim 1, wherein the particles are dimensionally stable.
 15. The fiber strand according to claim 1, wherein the particles are non-waxy particles.
 16. The fiber strand according to claim 1, wherein the particles have a Mohs' hardness value of no greater than that of the at least one fiber.
 17. The fiber strand according to claim 1, wherein the particles are thermally conductive.
 18. The fiber strand according to claim 1, wherein the particles are electrically insulative.
 19. The fiber strand according to claim 1, wherein the particles have an average particle size ranging up to 1000 micrometers, measured using laser scattering techniques.
 20. The fiber strand according to claim 19, wherein the particles have an average particle size ranging from 0.1 to 25 micrometers, measured using laser scattering techniques.
 21. The fiber strand according to claim 1, wherein the particles are selected from polymeric organic materials, non-polymeric organic materials, polymeric in organic materials, non-polymeric in organic materials, composite materials and mixtures thereof.
 22. The fiber strand according to claim 21, wherein the particles comprise non-polymeric inorganic materials selected from graphite, metals, oxides, carbides, nitrides, borides, sulfides, silicates, carbonates, sulfates, hydroxides and mixtures thereof.
 23. The fiber strand according to claim 22, wherein the particles comprisehexagonal boron nitride.
 24. The fiber strand according to claim 21, wherein the particles comprise at least one organic polymeric material selected from thermosetting polymeric materials and thermoplastic polymeric materials.
 25. The fiber strand according to claim 24, wherein the particles comprise at least one thermoplastic polymeric material selected from acrylic polymers, vinyl polymers, thermoplastic polyesters, polyolefins, polyamides and thermoplastic polyurethanes.
 26. The fiber strand according to claim 25, wherein the particles compriseat least one acrylic copolymer of styrene and acrylic monomer.
 27. The fiber stand according to claim 24, wherein the particles comprise at least one thermosetting polymeric material selected from thermosetting polyesters, vinyl esters, epoxy materials, phenolics, aminoplasts and thermosetting polyurethanes.
 28. The fiber strand according to claim 1, wherein the particles comprise at least one hollow particle.
 29. The fiber strand according to claim 28, wherein the at least one hollow particle comprises a copolymer of styrene and acrylic monomer.
 30. The fiber strand according to claim 1, wherein the particles compriseboron nitride.
 31. The fiber strand according to claim 1, wherein the particles are first particles and the forming size composition further comprises a plurality of additional discrete particles different from the first particles.
 32. The fiber strand according to claim 1, wherein the particles comprise hexagonal boron nitride particles and acrylic copolymer particles.
 33. The fiber strand according to claim 1, wherein the particles compriseat least one solid lubricant material.
 34. The fiber strand according to claim 33, wherein the particles compriseat least one inorganic solid lubricant material having a lamellar structure.
 35. The fiber strands according to claim 1, wherein the particles have a lamellar structure.
 36. The fiber strands according to claim 35, wherein the particles are selected from boron nitride, graphite, metal dichalcogenides, mica, talc, gypsum, kaolinite, calcite, cadmium iodide, silver sulfide, and mixtures thereof.
 37. The fiber strands according to claim 36, wherein the metal dichalcogenide particles are selected from molybdenum disulfide, molybdenum diselenide, tantalum disulfide, tantalum diselenide, tungsten disulfide, tungsten diselenide, and mixtures thereof.
 38. The fiber strand according to claim 1, wherein the particles comprise at least one inorganic, non-hydratable material.
 39. The fiber strand according to claim 1, wherein the particles are selected from hydratable inorganic material, hydrated inorganic material, and mixtures thereof.
 40. The fiber strand according to claim 1, wherein the particles are present in the forming size composition in an amount ranging from 1 to 30 weight percent of the sizing composition on a total solids basis.
 41. The fiber strand according to claim 40, wherein the particles are present in the forming size composition in an amount ranging from 1 to 20 weight percent of the sizing composition on a total solids basis.
 42. A fabric comprising at least one fiber strand according to claim
 29. 43. A fabric comprising at least one fiber strand according to claim
 30. 44. A fabric comprising at least one fiber strand according to claim
 32. 45. A coated fiber strand comprising at least one fiber having a residue of an aqueous forming size composition applied to at least a portion of a surface of the at least one fiber, the aqueous forming size composition comprising: (a) at least one starch; (b) at least one film-forming material; (c) at least one lubricant; and (d) a plurality of discrete particles having a Mohs hardness of no greater than that of the at least one fiber.
 46. A fabric comprising a plurality of fiber strands comprising at least one fiber having a residue of an aqueous forming size composition applied to at least a portion of a surface of the at least one fiber, the aqueous forming size composition comprising: (a) at least one starch; (b) at least one film-forming material; (c) at least one lubricant; and (d) a plurality of discrete particles that provide interstitial space between the at least one fiber and at least one adjacent fiber sufficient to allow wet out of the fiber strand.
 47. The fabric according to claim 46, wherein the strand is selected from twisted glass fiber strand and non-twisted glass fiber strand and the fabric is selected from woven fabrics, nonwoven fabrics and knitted fabrics.
 48. An electronic support comprising the fabric according to claim
 46. 